Table of Contents The notional amounts for outstanding derivative instruments provide one measure of the transaction volume outstanding and do not represent the amount of the Company’s exposure to credit or market loss.
The credit risk amounts represent the Company’s gross exposure to potential accounting loss on derivative instruments that are outstanding or unsettled if all counterparties failed to perform according to the terms of the contract, based on then-current currency or interest rates at each respective date.
The Company’s exposure to credit loss and market risk will vary over time as currency and interest rates change.
Although the table above reflects the notional and credit risk amounts of the Company’s derivative instruments, it does not reflect the gains or losses associated with the exposures and transactions that the instruments are intended to hedge.
The amounts ultimately realized upon settlement of these financial instruments, together with the gains and losses on the underlying exposures, will depend on actual market conditions during the remaining life of the instruments.
The Company generally enters into master netting arrangements, which are designed to reduce credit risk by permitting net settlement of transactions with the same counterparty.
To further limit credit risk, the Company generally enters into collateral security arrangements that provide for collateral to be received or posted when the net fair value of certain financial instruments fluctuates from contractually established thresholds.
The Company presents its derivative assets and derivative liabilities at their gross fair values in its Consolidated Balance Sheets.
The net cash collateral received by the Company related to derivative instruments under its collateral security arrangements was $1.0 billion as of September 26, 2015 and $2.1 billion as of September 27, 2014.
Under master netting arrangements with the respective counterparties to the Company’s derivative contracts, the Company is allowed to net settle transactions with a single net amount payable by one party to the other.
As of September 26, 2015 and September 27, 2014, the potential effects of these rights of set-off associated with the Company’s derivative contracts, including the effects of collateral, would be a reduction to both derivative assets and derivative liabilities of $2.2 billion and $1.6 billion, respectively, resulting in net derivative liabilities of $78 million and $549 million, respectively.
Accounts Receivable Trade Receivables The Company has considerable trade receivables outstanding with its third-party cellular network carriers, wholesalers, retailers, value-added resellers, small and mid-sized businesses and education, enterprise and government customers.
The Company generally does not require collateral from its customers; however, the Company will require collateral in certain instances to limit credit risk.
In addition, when possible, the Company attempts to limit credit risk on trade receivables with credit insurance for certain customers or by requiring third-party financing, loans or leases to support credit exposure.
These credit-financing arrangements are directly between the third-party financing company and the end customer.
As such, the Company generally does not assume any recourse or credit risk sharing related to any of these arrangements.
As of September 26, 2015, the Company had one customer that represented 10% or more of total trade receivables, which accounted for 12%.
As of September 27, 2014, the Company had two customers that represented 10% or more of total trade receivables, one of which accounted for 16% and the other 13%.
The Company’s cellular network carriers accounted for 71% and 72% of trade receivables as of September 26, 2015 and September 27, 2014, respectively.
Vendor Non-Trade Receivables The Company has non-trade receivables from certain of its manufacturing vendors resulting from the sale of components to these vendors who manufacture sub-assemblies or assemble final products for the Company.
The Company purchases these components directly from suppliers.
Vendor non-trade receivables from three of the Company’s vendors accounted for 38%, 18% and 14% of total vendor non-trade receivables as of September 26, 2015 and three of the Company’s vendors accounted for 51%, 16% and 14% of total vendor non-trade receivables as of September 27, 2014.
Note 3 – Consolidated Financial Statement Details The following tables show the Company’s consolidated financial statement details as of September 26, 2015 and September 27, 2014 (in millions): Property, Plant and Equipment, Net
## Table 0 ##
Apple Inc.  | 2015 Form 10-K | 53
Remediation efforts recorded are as follows:
## Table 1 ##
The Company did not record any insurance recoveries during 2011 or have any receivables for insurance recoveries related to these matters as of December 31, 2011.
As of December 31, 2011 and 2010, there were receivables of $6 million and $7 million, respectively, from the former owner of the Company's Spondon, Derby, United Kingdom acetate flake, tow and film business, which was acquired in 2007, and is included in the Company's Consumer Specialties segment.
German InfraServ Entities On January 1, 1997, coinciding with a reorganization of the Hoechst businesses in Germany, real estate service companies (“InfraServ Entities”) were created to own directly the land and property and to provide various technical and administrative services at each of the manufacturing locations.
The Company owns manufacturing facilities at the InfraServ location in Frankfurt am Main-Hoechst, Germany and holds equity interests in the companies which own and operate the former Hoechst sites in Frankfurt am Main-Hoechst, Gendorf and Knapsack, all of which are located in Germany.
InfraServ Entities are liable for any residual contamination and other pollution because they own the real estate on which the individual facilities operate.
In addition, Hoechst, and its legal successors, as the responsible party under German public law, is liable to third parties for all environmental damage that occurred while it was still the owner of the plants and real estate (Note 23).
The contribution agreements entered into in 1997 between Hoechst and the respective operating companies, as part of the divestiture of these companies, provide that the operating companies will indemnify Hoechst, and its legal successors, against environmental liabilities resulting from the transferred businesses.
Additionally, the InfraServ Entities have agreed to indemnify Hoechst, and its legal successors, against any environmental liability arising out of or in connection with environmental pollution of any site.
The InfraServ partnership agreements provide that, as between the partners, each partner is responsible for any contamination caused predominantly by such partner.
Any liability, which cannot be attributed to an InfraServ partner and for which no third party is responsible, is required to be borne by the InfraServ partnership.
If an InfraServ partner defaults on its respective indemnification obligations to eliminate residual contamination, the owners of the remaining participation in the InfraServ companies have agreed to fund such liabilities, subject to a number of limitations.
To the extent that any liabilities are not satisfied by either the InfraServ Entities or their owners, these liabilities are to be borne by the Company in accordance with the demerger agreement.
However, Hoechst, and its legal successors, will reimburse the Company for two-thirds of any such costs.
Likewise, in certain circumstances the Company could be responsible for the elimination of residual contamination on several sites that were not transferred to InfraServ companies, in which case Hoechst, and its legal successors, must also reimburse the Company for two-thirds of any costs so incurred.
The German InfraServ Entities are owned partially by the Company (Note 8), as noted below, and the remaining ownership is held by various other companies.
The Company's ownership interest and environmental liability participation percentages for such liabilities which cannot be attributed to an InfraServ partner are as follows:
## Table 2 ##
(1) Gross reserves maintained by the respective InfraServ entity
PART II DUKE ENERGY CORPORATION ?
DUKE ENERGY CAROLINAS, LLC ?
PROGRESS ENERGY, INC.  ?
DUKE ENERGY PROGRESS, LLC ?
DUKE ENERGY FLORIDA, LLC ?
DUKE ENERGY OHIO, INC.  ?
DUKE ENERGY INDIANA, LLC ?
PIEDMONT NATURAL GAS COMPANY, INC.
Combined Notes to Consolidated Financial Statements – (Continued) 2.
ACQUISITIONS AND DISPOSITIONS ACQUISITIONS The Duke Energy Registrants consolidate assets and liabilities from acquisitions as of the purchase date and include earnings from acquisitions in consolidated earnings after the purchase date.2016 Acquisition of Piedmont Natural Gas On October 3, 2016, Duke Energy acquired all outstanding common stock of Piedmont for a total cash purchase price of $5.0 billion and assumed Piedmont’s existing long-term debt, which had a fair value of approximately $2.0 billion at the time of the acquisition.
The acquisition provides a foundation for Duke Energy to establish a broader, long-term strategic natural gas infrastructure platform to complement its existing natural gas pipeline investments and regulated natural gas business in the Midwest.
In connection with the closing of the acquisition, Piedmont became a wholly owned subsidiary of Duke Energy.
Purchase Price Allocation The purchase price allocation of the Piedmont acquisition is as follows:
## Table 3 ##
ignificant estimates and assumptions that are judgmental in nature, including the amount and timing of projected future cash flows, discount rates reflecting risk inherent in the future cash flows and market prices of long-term debt.
The majority of Piedmont’s operations are subject to the rate-setting authority of the NCUC, the PSCSC and the TPUC and are accounted for pursuant to accounting guidance for regulated operations.
The rate-setting and cost recovery provisions currently in place for Piedmont’s regulated operations provide revenues derived from costs, including a return on investment of assets and liabilities included in rate base.
Thus, the fair value of Piedmont’s assets and liabilities subject to these rate-setting provisions approximates the pre-acquisition carrying values and does not reflect any net valuation adjustments.
The significant assets and liabilities for which valuation adjustments were reflected within the purchase price allocation include the acquired equity method investments and long-term debt.
The difference between the fair value and the pre-merger carrying values of long-term debt for regulated operations was recorded as a regulatory asset.
The excess of the purchase price over the fair value of Piedmont’s assets and liabilities on the acquisition date was recorded as goodwill.
The goodwill reflects the value paid by Duke Energy primarily for establishing a broader, long-term strategic natural gas infrastructure growth platform, an improved risk profile and expected synergies resulting from the combined entities.
Under Securities and Exchange Commission (SEC) regulations, Duke Energy elected not to apply push down accounting to the stand-alone Piedmont financial statements.
Accounting Charges Related to the Acquisition Duke Energy incurred pretax non-recurring transaction and integration costs associated with the acquisition of $103 million, $439 million and $9 million for the years ended December 31, 2017, 2016 and 2015, respectively.
Amounts recorded on the Consolidated Statements of Operations in 2017 were primarily system integration costs of $71 million related to combining the various operational and financial systems of Duke Energy and Piedmont, including a one-time software impairment resulting from planned accounting system and process integration.
A $7 million charge was recorded within Impairment Charges, with the remaining $64 million recorded within Operation, maintenance and other.
Amounts recorded in 2016 include: ?
Interest expense of $234 million related to the acquisition financing, including realized losses on forward-starting interest rate swaps of $190 million.
See Note 14 for additional information on the swaps.  ?
Charges of $104 million related to commitments made in conjunction with the transaction, including charitable contributions and a onetime bill credit to Piedmont customers.
$10 million was recorded as a reduction in Operating Revenues, with the remaining $94 million recorded within Operation, maintenance and other.  ?
Other transaction and integration costs of $101 million recorded to Operation, maintenance and other, including professional fees and severance.
The majority of transition and integration activities are expected to be completed by the end of 2018.
Pro Forma Financial Information The following unaudited pro forma financial information reflects the combined results of operations of Duke Energy and Piedmont as if the merger had occurred as of January 1, 2015.
The pro forma financial information does not include potential cost savings, intercompany revenues, Piedmont’s earnings from a certain equity method investment sold immediately prior to the merger or non-recurring transaction and integration costs incurred by Duke Energy and Piedmont.
The after-tax non-recurring transaction and integration costs incurred by Duke Energy and Piedmont were $279 million and $19 million for the years ended December 31, 2016, and 2015, respectively.
This information has been presented for illustrative purposes only and is not necessarily indicative of the consolidated results of operations that would have been achieved or the future consolidated results of operations of Duke Energy
## Table 4 ##
PART II to the Consolidated Financial Statements, “Regulatory Matters,” for additional information.
Rapidly rising interest rates without timely or adequate updates to the regulated allowed return on equity or failure to achieve the anticipated benefits of the Piedmont merger, including cost savings and growth targets, could significantly impact the estimated fair value of reporting units in Gas Utilities and Infrastructure.
In the event of a significant decline in the estimated fair value of the reporting units, goodwill impairment charges could be recorded.
The carrying value of goodwill within Gas Utilities and Infrastructure was approximately $1,924 million at December 31, 2017.
Within this Item 7, see the Tax Cuts and Jobs Act above as well as Liquidity and Capital Resources below for risks associated with the Tax Act.
Commercial Renewables
## Table 5 ##
Year Ended December 31, 2017, as Compared to 2016 Commercial Renewables’ higher earnings were primarily due to the Tax Act, partially offset by pretax impairment charges.
The following is a detailed discussion of the variance drivers by line item.
Operating Revenues.
The decrease was primarily due to lower engineering, procurement and construction revenues from REC Solar, a California-based provider of solar installations acquired by Duke Energy in 2015.
Operating Expenses.
The increase was primarily due to $99 million in pretax impairment charges in the current year related to a wholly owned noncontracted wind project and other investments and higher expenses associated with new wind and solar projects, partially offset by lower operations and maintenance expense at REC Solar due to fewer projects under construction.
See Notes 10 and 11 to the Consolidated Financial Statements, “Property, Plant and Equipment” and “Goodwill and Intangible Assets,” respectively, for additional information.
Other Income and Expenses.
The variance was primarily due to a $71 million pretax impairment charge in the prior year related to certain equity method investments.
For additional information, see Note 12 to the Consolidated Financial Statements, “Investments in Unconsolidated Affiliates.
” Interest Expense.
The variance was primarily due to new project financings and less capitalized interest due to fewer projects under construction.
Income Tax Benefit.
The variance was primarily due to the impact of the Tax Act and higher production tax credits (PTCs), partially offset by lower investment tax credits (ITCs).
See the Tax Cuts and Jobs Act section above for additional information on the Tax Act and the impact on the effective tax rate.
Year Ended December 31, 2016, as Compared to 2015 Commercial Renewables’ lower earnings were primarily due to an impairment charge related to certain equity method investments in wind projects, partially offset by new wind and solar generation placed in service and improved wind production.
The following is a detailed discussion of variance drivers by line item.
Operating Revenues.
The variance was primarily due to a $135 million increase due to growth of REC Solar and a $66 million increase from new wind and solar generation placed in service and improved wind production.
Operating Expenses.
The variance was primarily due to a $130 million increase in operating expenses due to growth of REC Solar and a $36 million increase in operating expenses due to new wind and solar generation placed in service.
Other Income and Expenses.
The variance was due to a $71 million pretax impairment charge related to certain equity method investments in wind projects.
See Note 12 to the Consolidated Financial Statements, “Investments in Unconsolidated Affiliates,” for additional information.

<table><tr><td></td><td>2015</td><td>2014</td></tr><tr><td>Land and buildings</td><td>$6,956</td><td>$4,863</td></tr><tr><td>Machinery, equipment and internal-use software</td><td>37,038</td><td>29,639</td></tr><tr><td>Leasehold improvements</td><td>5,263</td><td>4,513</td></tr><tr><td>Gross property, plant and equipment</td><td>49,257</td><td>39,015</td></tr><tr><td>Accumulated depreciation and amortization</td><td>-26,786</td><td>-18,391</td></tr><tr><td>Total property, plant and equipment, net</td><td>$22,471</td><td>$20,624</td></tr></table>
<table><tr><td></td><td colspan="3">Year Ended December 31,</td></tr><tr><td></td><td>2011</td><td>2010</td><td>2009</td></tr><tr><td></td><td colspan="3">(In $ millions)</td></tr><tr><td>Cost of sales</td><td>2</td><td>1</td><td>9</td></tr><tr><td>Selling, general and administrative expenses</td><td>6</td><td>8</td><td>6</td></tr></table>
<table><tr><td></td><td colspan="3">As of December 31, 2011</td></tr><tr><td></td><td>Ownership</td><td>Liability</td><td>Reserves<sup>-1</sup></td></tr><tr><td></td><td colspan="2">(In percentages)</td><td>(In $ millions)</td></tr><tr><td>InfraServ GmbH & Co. Gendorf KG</td><td>39</td><td>10</td><td>11</td></tr><tr><td>InfraServ GmbH & Co. Knapsack KG</td><td>27</td><td>22</td><td>1</td></tr><tr><td>InfraServ GmbH & Co. Hoechst KG</td><td>32</td><td>40</td><td>71</td></tr></table>
<table><tr><td>Current assets</td><td>$497</td></tr><tr><td>Property, plant and equipment, net</td><td>4,714</td></tr><tr><td>Goodwill</td><td>3,353</td></tr><tr><td>Other long-term assets</td><td>804</td></tr><tr><td>Total assets</td><td>9,368</td></tr><tr><td>Current liabilities, including current maturities of long-term debt</td><td>576</td></tr><tr><td>Long-term liabilities</td><td>1,790</td></tr><tr><td>Long-term debt</td><td>2,002</td></tr><tr><td>Total liabilities</td><td>4,368</td></tr><tr><td>Total purchase price</td><td>$5,000</td></tr></table>
<table><tr><td></td><td colspan="2">Years Ended December 31,</td></tr><tr><td>(in millions)</td><td>2016</td><td>2015</td></tr><tr><td>Operating Revenues</td><td>$23,504</td><td>$23,570</td></tr><tr><td>Net Income Attributable to Duke Energy Corporation</td><td>2,442</td><td>2,877</td></tr></table>
<table><tr><td></td><td colspan="5">Years Ended December 31,</td></tr><tr><td>(in millions)</td><td>2017</td><td>2016</td><td>Variance 2017 vs. 2016</td><td>2015</td><td>Variance 2016 vs. 2015</td></tr><tr><td>Operating Revenues</td><td>$460</td><td>$484</td><td>$-24</td><td>$286</td><td>$198</td></tr><tr><td>Operating Expenses</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Operation, maintenance and other</td><td>267</td><td>337</td><td>-70</td><td>197</td><td>140</td></tr><tr><td>Depreciation and amortization</td><td>155</td><td>130</td><td>25</td><td>104</td><td>26</td></tr><tr><td>Property and other taxes</td><td>33</td><td>25</td><td>8</td><td>18</td><td>7</td></tr><tr><td>Impairment charges</td><td>99</td><td>—</td><td>99</td><td>3</td><td>-3</td></tr><tr><td>Total operating expenses</td><td>554</td><td>492</td><td>62</td><td>322</td><td>170</td></tr><tr><td>Gains on Sales of Other Assets and Other, net</td><td>1</td><td>5</td><td>-4</td><td>1</td><td>4</td></tr><tr><td>Operating Loss</td><td>-93</td><td>-3</td><td>-90</td><td>-35</td><td>32</td></tr><tr><td>Other Income and Expenses</td><td>-12</td><td>-83</td><td>71</td><td>2</td><td>-85</td></tr><tr><td>Interest Expense</td><td>87</td><td>53</td><td>34</td><td>44</td><td>9</td></tr><tr><td>Loss Before Income Taxes</td><td>-192</td><td>-139</td><td>-53</td><td>-77</td><td>-62</td></tr><tr><td>Income Tax Benefit</td><td>-628</td><td>-160</td><td>-468</td><td>-128</td><td>-32</td></tr><tr><td>Less: Loss Attributable to Noncontrolling Interests</td><td>-5</td><td>-2</td><td>-3</td><td>-1</td><td>-1</td></tr><tr><td>Segment Income</td><td>$441</td><td>$23</td><td>$418</td><td>$52</td><td>$-29</td></tr><tr><td>Renewable plant production, GWh</td><td>8,260</td><td>7,446</td><td>814</td><td>5,577</td><td>1,869</td></tr><tr><td>Net proportional MW capacity in operation</td><td>2,907</td><td>2,892</td><td>15</td><td>1,943</td><td>949</td></tr></table>

Question: as of september 27 , 2014 , what percentage of total trade receivables did the company's two largest customers account for ?
Answer: 29