Debt (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	$ 446,000,000us-gaap_LineOfCredit	$ 649,000,000us-gaap_LineOfCredit
Long-term debt	2,892,000,000us-gaap_LongTermDebtNoncurrent	3,694,000,000us-gaap_LongTermDebtNoncurrent
Net proceeds from issuance of Senior Notes		990,000,000
Early Repayment of Subordinated Debt	600,000,000	0	875,000,000
Payments Of Debt Extinguishment Costs	14,000,000
Write off of Deferred Debt Issuance Cost	3,000,000
Debt (Textuals)
Line of Credit Facility, Maximum Borrowing Capacity	1,400,000,000
Largest individual loan commitment by any lender of total commitments	14.00%nfx_LargestCommitmentOfTotalCommitments
Percentage of basis points to be added for calculation of interest rate	0.50%
Percent added to prime rate based on grid of our debt rating	0.75%
Percentage added to LIBOR based on grid of our debt rating	1.75%nfx_PercentageAddedToLibor
Commitment fee percentage on unused capacity of line of credit	0.30%
Commitment fees incurred	4,000,000	3,000,000	3,000,000
Ratio of Indebtedness to Net Capital 1	0.6
Ratio of total debt to earnings before gain or loss on disposition of assets, interest expense, income taxes and noncash items	3.0
Issuance fees percentage on letter of credit	0.20%
Percentage based on a grid of our debt rating on which letters of credit fees are based.	1.75%
Line of Credit Facility, Current Borrowing Capacity	94,000,000
Discount On Notes [Member]
Debt Instrument [Line Items]
Long-term debt	(4,000,000)	(5,000,000)
6.875% Senior Subordinated Notes due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt	700,000,000	700,000,000
Debt Instrument, Interest Rate, Stated Percentage	6.875%	6.875%
7.125% Senior Subordinated Notes due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt	0	600,000,000
Debt Instrument, Interest Rate, Stated Percentage	7.125%	7.125%
Early Repayment of Subordinated Debt	600,000,000
Total senior unsecured debt
Debt Instrument [Line Items]
Long-term debt	2,196,000,000	2,399,000,000
5.625% Senior Notes Due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	1,000,000,000	1,000,000,000
Debt Instrument, Interest Rate, Stated Percentage	5.625%	5.625%
5.75 %Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	750,000,000	750,000,000
Debt Instrument, Interest Rate, Stated Percentage	5.75%	5.75%
Money market lines of credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	101,000,000	64,000,000
Revolving Credit Facility Libor Based Loans [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	$ 345,000,000	$ 585,000,000

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Largest individual loan commitment percent of total loan commitments by any one lender for revolving credit facility.

+ References

No definition available.

+ Details

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- Definition

Percentage added to the prime rate based upon a grid of our debt rating in determining the interest rate on borrowings under our credit facility (one of two options).

+ References

No definition available.

+ Details

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- Definition

Percentage added to LIBOR based upon a grid of our debt rating to determine the interest rate on borrowings under our credit facility (one of two options).

+ References

No definition available.

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- Definition

Percentage based on a grid of our debt rating on which letters of credit fees are based.

+ References

No definition available.

+ Details

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- Definition

Percentage on which issuance fees on Letter of credit are subject

+ References

No definition available.

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- Definition

Ratio of total debt to earnings before gain or loss on disposition of assets, interest expense, income taxes and noncash items that must be maintained due to restrictive covenants on our credit facility.

+ References

No definition available.

+ Details

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

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- Definition

The cash outflow from the repayment of long-term borrowing where a lender is placed in a lien position behind debt having a higher priority of repayment (senior) in case of liquidation of the entity's assets before its maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (b)

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-Subparagraph (SX 210.7-03.16)

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+ Details

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- Definition

Amount of the fee for available but unused credit capacity under the credit facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

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- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

+ Details

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities). Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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- Definition

The cash outflow for incremental, external costs directly pertaining to an early extinguishment of debt, including legal costs and prepayment penalties, and excluding interest and repayment of debt principal.

+ References

No definition available.

+ Details

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- Definition

The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination.

+ References

No definition available.

+ Details

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- Definition

Indebtedness divided by net capital.

+ References

No definition available.

+ Details

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- Definition

Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

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-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.8)

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