| **Stock-Based and Other Compensation Plans Stock-Based and Other Compensation Plans (Details 3) (Restricted Stock [Member])** | 12 Months Ended                                                                                                                                                         |
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| Restricted Stock [Member]                                                                                                     |                                                                                                                                                                    |   |
| **Share-based Compensation Arrangement by Share-based Payment Award [Line Items]**                                            |                                                                                                                                                                    |   |
| Number of simulations                                                                                                         | 500,000nbl_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberofSimulationsUsedToDetermineAssumptions/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember | 500,000nbl_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberofSimulationsUsedToDetermineAssumptions/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |
| Expected volatility (in hundredths)                                                                                           | 30.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember | 30.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |
| Risk-free rate (in hundredths)                                                                                                | 0.70%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember    | 0.40%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |

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| - Definition
Share Based Compensation Arrangement By Share Based Payment, Award, Number of Simulations Used To Determine Assumptions
+ References
No definition available.
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| - Definition
The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901
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| - Definition
The risk-free interest rate assumption that is used in valuing an option on its own shares.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iv) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901
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