| **Regulatory Matters - Rate and Regulatory Actions (Details) - USD ($) $ in Thousands**                                        | 1 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            | 6 Months Ended | 9 Months Ended |
|--------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Public Utilities, Rate Matters, Approved [Abstract]**                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| Increase (Decrease) Regulatory liabilities                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           | $ 13,377       | $ (5,180) |
| North Carolina Utilities Commission | IMR Petition Filed November 2015                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| **Public Utilities, Rate Matters, Requested [Abstract]**                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| Annual Requested Integrity Management Rider, Amount                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           | 40,900         |   |
| North Carolina Utilities Commission | IMR Petition Filed May 2016                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| **Public Utilities, Rate Matters, Requested [Abstract]**                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| Public Utilities Requested Rate Increase (Decrease) Amount                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           | 7,400          |   |
| North Carolina Utilities Commission | Proposed Stipulation And Settlement Agreement Filed June 2016                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| **Public Utilities, Rate Matters, Approved [Abstract]**                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| Annual Charitable Contributions Commitment                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           | 17,500         |   |
| Low-Income Household Energy Assistance and Workforce Development Programs Commitment                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           | 7,500          |   |
| North Carolina Utilities Commission | Subsequent Event | Joint Proposed Order Filed August 2016                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| **Public Utilities, Rate Matters, Approved [Abstract]**                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| Public Utilities, Disclosure of Regulatory Matters Pending                                                                     | A hearing was held on July 18 and 19, 2016. On August 25, 2016, we, Duke Energy and the NCUC Public Staff filed a joint proposed order pursuant to the NCUC's procedural schedule. We are waiting on a ruling from the NCUC at this time.                                                                                                                                                                                                                                                                                                                                                                                                                                                 |           |           |   |
| North Carolina Utilities Commission | Subsequent Event | Gas Cost Purchasing Review August 2016                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| **Public Utilities, Rate Matters, Approved [Abstract]**                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| Public Utilities, Disclosure of Rate Matters                                                                                   | In August 2016, we filed testimony with the NCUC in support of our gas cost purchasing and accounting practices for the twelve months ended May 31, 2016. A hearing has been scheduled for October 3, 2016.                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |           |           |   |
| North Carolina Utilities Commission | Amounts due to customers | Proposed Stipulation And Settlement Agreement Filed June 2016 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| **Public Utilities, Rate Matters, Approved [Abstract]**                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| Increase (Decrease) Regulatory liabilities                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           | $ 10,000       |   |
| Public Service Commission of South Carolina | Subsequent Event | Approved Annual Purchase Gas Adjustment August 2016           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| **Public Utilities, Rate Matters, Approved [Abstract]**                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| Public Utilities, Disclosure of Rate Matters                                                                                   | In June 2016, we filed testimony with the Public Service Commission of South Carolina (PSCSC) in support of our annual review of purchased gas adjustment and gas purchasing policies for the twelve months ended March 31, 2016. In June 2016, a settlement agreement with the Office of Regulatory Staff (ORS) was filed. A hearing was held on July 14, 2016. In August 2016, the PSCSC approved the settlement agreement finding that our gas purchasing policies were reasonable and prudent, that we properly adhered to the gas cost recovery provisions of our tariff and relevant PSCSC orders and that we managed our hedging program in a manner consistent with PSCSC orders. |           |           |   |
| Public Service Commission of South Carolina | Subsequent Event | Requested Rate Stabilization Agreement June 2016              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| **Public Utilities, Rate Matters, Approved [Abstract]**                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| Public Utilities, Disclosure of Rate Matters                                                                                   | In June 2016, we filed with the PSCSC a quarterly monitoring report for the twelve months ended March 31, 2016 and a cost and revenue study under the Rate Stabilization Act requesting a change in rates. In August 2016, a settlement agreement was filed with the ORS stipulating an $8.3 million annual increase in margin based on a return on equity of 10.2%, effective November 1, 2016. We are waiting on a ruling from the PSCSC at this time.                                                                                                                                                                                                                                  |           |           |   |
| **Public Utilities, Rate Matters, Requested [Abstract]**                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| Public Utilities Requested Rate Increase (Decrease) Amount                                                                     | $ 8,300                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |           |           |   |
| Public Utilities, Requested Return on Equity, Percentage                                                                       | 10.20%                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |           |           |   |
| Tennessee Regulatory Authority | Subsequent Event | Actual Cost Adjustment                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| **Public Utilities, Rate Matters, Approved [Abstract]**                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| Public Utilities, Disclosure of Rate Matters                                                                                   | In August 2016, we filed an annual report for the twelve months ended June 30, 2016 with the TRA that reflected the transactions in the deferred gas cost account for the ACA mechanism. We are waiting on a ruling from the TRA at this time.                                                                                                                                                                                                                                                                                                                                                                                                                                            |           |           |   |
| Tennessee Regulatory Authority | Subsequent Event | Tennessee Incentive Plan                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| **Public Utilities, Rate Matters, Approved [Abstract]**                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| Public Utilities, Disclosure of Rate Matters                                                                                   | In August 2016, we filed an annual report with the TRA reflecting the shared gas cost savings from gains and losses derived from gas purchase benchmarking and secondary market transactions for the twelve months ended June 30, 2016 under the Tennessee Incentive Plan (TIP). We are waiting on a ruling from the TRA at this time.                                                                                                                                                                                                                                                                                                                                                    |           |           |   |
| Tennessee Regulatory Authority | Subsequent Event | Weather Normalization Adjustment Rider                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| **Public Utilities, Rate Matters, Approved [Abstract]**                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| Public Utilities, Disclosure of Rate Matters                                                                                   | In July 2016, the TRA Staff filed its compliance audit report for operation of our Weather Normalization Adjustment (WNA) rider during the 2015 – 2016 heating season, concluding that we had correctly implemented the WNA rider in all material aspects. The TRA Staff identified an immaterial error that resulted in an under-collection of our WNA revenues and recommended a correcting adjustment through the ACA mechanism which we recorded in August 2016. In August 2016, the TRA approved and adopted the TRA Staff’s compliance audit report.                                                                                                                    |           |           |   |
| NORTH CAROLINA                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| **Public Utilities, Rate Matters, Approved [Abstract]**                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |           |           |   |
| Capital Investments In Integrity and Safety Projects                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      | $ 74,900       |           |   |

| X                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Funding provided by combined company for annual charitable contributions for set duration after the acquisition.
+ References
No definition available.
+ Details**Name:**pny_AnnualCharitableContributionsCommitment**Namespace Prefix:**pny_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of the Company's capital investments in integrity and safety projects.
+ References
No definition available.
+ Details**Name:**pny_CapitalInvestmentsInIntegrityandSafetyProjects**Namespace Prefix:**pny_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The annual Integrity Management Riders (IMRs) margin revenues requested.
+ References
No definition available.
+ Details**Name:**pny_IntegrityManagementRiderAmount**Namespace Prefix:**pny_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Commitment by the combined company for low-income household energy assistance and workforce development programs.
+ References
No definition available.
+ Details**Name:**pny_LowIncomeHouseholdEnergyAssistanceandWorkforceDevelopmentProgramsCommitment**Namespace Prefix:**pny_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The increase (decrease) during the reporting period in regulated liabilities. Regulated liabilities are created when regulatory agency permits an entity to defer revenues to the balance sheet.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585
+ Details**Name:**us-gaap_IncreaseDecreaseInRegulatoryLiabilities**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Describes all of the specific events that have or may impact rates and amortization of regulatory assets and liabilities (for example, pending or recently concluded regulatory proceedings, environmental requirements). Specifics may include quantifications related to rates, costs, and earnings. Events may relate to rate moratoriums or price caps.
+ References
No definition available.
+ Details**Name:**us-gaap_PublicUtilitiesDisclosureOfRateMatters**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Describes all of the specific regulatory matters that are pending, including the regulatory authorities involved and the potential impacts.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section 55 -Paragraph 29 -URI http://asc.fasb.org/extlink&oid=6591472&loc=d3e46731-110388Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14394-108349Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section 55 -Paragraph 16 -URI http://asc.fasb.org/extlink&oid=6591472&loc=d3e46596-110388Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 20 -Section 40 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=64845297&loc=d3e42103-110369Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section 55 -Paragraph 25 -URI http://asc.fasb.org/extlink&oid=6591472&loc=d3e46694-110388Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section 55 -Paragraph 27 -URI http://asc.fasb.org/extlink&oid=6591472&loc=d3e46721-110388Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section 55 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=6591472&loc=d3e46641-110388Reference 10: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section 55 -Paragraph 21 -URI http://asc.fasb.org/extlink&oid=6591472&loc=d3e46666-110388Reference 11: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=6591472&loc=d3e46613-110388Reference 12: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section 55 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=6591472&loc=d3e46726-110388Reference 13: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section 55 -Paragraph 23 -URI http://asc.fasb.org/extlink&oid=6591472&loc=d3e46676-110388Reference 14: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section 55 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=6591472&loc=d3e46689-110388Reference 15: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14453-108349Reference 16: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section 55 -Paragraph 22 -URI http://asc.fasb.org/extlink&oid=6591472&loc=d3e46671-110388
+ Details**Name:**us-gaap_PublicUtilitiesDisclosureOfRegulatoryMattersPending**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                    |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - References
No definition available.
+ Details**Name:**us-gaap_PublicUtilitiesRateMattersApprovedAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - References
No definition available.
+ Details**Name:**us-gaap_PublicUtilitiesRateMattersRequestedAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of public utility's requested rate increase (decrease) with regulatory agency.
+ References
No definition available.
+ Details**Name:**us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of public utility's requested return on equity.
+ References
No definition available.
+ Details**Name:**us-gaap_PublicUtilitiesRequestedReturnOnEquityPercentage**Namespace Prefix:**us-gaap_**Data Type:**num:percentItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RegulatoryAgencyAxis=pny_NorthCarolinaUtilitiesCommissionMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pny_IMRPetitionFiledNovember2015Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pny_IMRPetitionFiledMay2016Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                        |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pny_ProposedStipulationAndSettlementAgreementFiledJune2016Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                     |
|-------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pny_JointProposedOrderFiledAugust2016Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pny_GasCostPurchasingReviewAugust2016Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RegulatoryLiabilityAxis=pny_AmountDueToCustomersMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RegulatoryAgencyAxis=pny_PublicServiceCommissionofSouthCarolinaMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                               |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pny_ApprovedAnnualPurchaseGasAdjustmentAugust2016Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pny_RequestedRateStabilizationAgreementJune2016Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RegulatoryAgencyAxis=pny_TennesseeRegulatoryAuthorityMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pny_ActualCostAdjustmentMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pny_TennesseeIncentivePlanMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pny_WeatherNormalizationAdjustmentRiderMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                 |
|-----------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_StatementGeographicalAxis=stpr_NC**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |