Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2017

Fair Value Disclosures [Abstract]

Fair value by measurement classification and type Table

The following table summarizes the valuation of our assets and liabilities that are measured at fair value on a recurring basis.

	Fair Value Measurement Classification
	Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1)			Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)			Total
	(In millions)
As of December 31, 2016:
Money market fund investments	$	320		$	—	$	—		$	320
Deferred compensation plan assets	6			—		—			6
Equity securities available-for-sale	9			—		—			9
Oil and gas derivative swap contracts	—			50		—			50
Oil and gas derivative option contracts	—			—		(75		)	(75		)
Stock-based compensation liability awards	(11		)	—		—			(11		)
Total	$	324		$	50	$	(75	)	$	299
As of March 31, 2017:
Money market fund investments	$	236		$	—	$	—		$	236
Deferred compensation plan assets	6			—		—			6
Equity securities available-for-sale	11			—		—			11
Oil and gas derivative swap contracts	—			71		—			71
Oil and gas derivative option contracts	—			—		(63		)	(63		)
Stock-based compensation liability awards	(12		)	—		—			(12		)
Total	$	241		$	71	$	(63	)	$	249

Fair value changes level 3 Table

The following table sets forth a reconciliation of changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy for the indicated periods.

	Derivatives
	(In millions)
Balance at January 1, 2016	$	(308	)
Unrealized gains (losses) included in earnings	(46		)
Purchases, issuances, sales and settlements:
Settlements	92
Transfers into Level 3	—
Transfers out of Level 3	—
Balance at March 31, 2016	$	(262	)
Change in unrealized gains or losses included in earnings relating to Level 3 instruments still held at March 31, 2016	$	(32	)
Balance at January 1, 2017	$	(75	)
Unrealized gains (losses) included in earnings	(6		)
Purchases, issuances, sales and settlements:
Settlements	18
Transfers into Level 3	—
Transfers out of Level 3	—
Balance at March 31, 2017	$	(63	)
Change in unrealized gains or losses included in earnings relating to Level 3 instruments still held at March 31, 2017	$	(4	)

Quantitative disclosures about unobservable inputs

	Estimated Fair Value Asset (Liability)			Quantitative Information about Level 3 Fair Value Measurements
Instrument Type				ValuationTechnique	Unobservable Input	Range
	(In millions)
Oil option contracts	$	(53	)	Modified Black-Scholes	Oil price volatility	22.57	%	—	118.40%
					Credit risk	0.01	%	—	1.25%
Natural gas option contracts	$	(10	)	Modified Black-Scholes	Natural gas price volatility	24.33	%	—	41.31%
					Credit risk	0.01	%	—	1.25%

Estimated fair value of the debt instrument at the balance sheet date

The estimated fair value of our notes, based on quoted prices in active markets (Level 1) as of the indicated dates, was as follows:

	March 31,   2017		December 31,   2016
	(In millions)
5¾% Senior Notes due 2022	$	796	$	789
5⅝% Senior Notes due 2024	1,054		1,044
5⅜% Senior Notes due 2026	731		714