Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2012

Table Text Block Supplement [Abstract]

Valuation of investments and financial instrument assets (liabilities) by pricing levels

	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, 2011:
Investments available-for-sale:
Equity securities	$	10	$	—	$	—	$	10
Auction rate securities		—		—		32		32
Oil and gas derivative swap contracts		—		66		(10)		56
Oil and gas derivative option contracts		—		—		81		81
Total	$	10	$	66	$	103	$	179
As of June 30, 2012:
Money market fund investments	$	430	$	—	$	—	$	430
Investments available-for-sale:
Equity securities		11		—		—		11
Auction rate securities		—		—		34		34
Oil and gas derivative swap contracts		—		25		(6)		19
Oil and gas derivative option contracts		—		—		191		191
Total	$	441	$	25	$	219	$	685

Reconciliation of changes in the fair value of financial assets and liabilities classified as Level 3 in the fair value hierarchy

			Investments		Derivatives		Total
			(In millions)
Balance at January 1, 2011			$	30	$	48	$	78
	Total realized or unrealized gains (losses):
		Included in earnings		—		(8)		(8)
		Included in other comprehensive income		5		—		5
	Purchases, issuances and settlements:
		Settlements		—		(26)		(26)
	Transfers in and out of Level 3			—		—		—
Balance at June 30, 2011			$	35	$	14	$	49
Change in unrealized losses included in earnings relating to
	investments and derivatives still held at June 30, 2011		$	—	$	(12)	$	(12)
Balance at January 1, 2012			$	32	$	71	$	103
	Total realized or unrealized gains (losses):
		Included in earnings		—		157		157
		Included in other comprehensive income		2		—		2
	Purchases, issuances and settlements:
		Settlements		—		(43)		(43)
	Transfers in and out of Level 3			—		—		—
Balance at June 30, 2012			$	34	$	185	$	219
Change in unrealized gains included in earnings relating to
	investments and derivatives still held at June 30, 2012		$	—	$	141	$	141

Quantitative Information about Level 3 Fair Value Measurements

	Estimated
	Fair Value		Quantitative Information about Level 3 Fair Value Measurements
	Asset		Valuation
Instrument Type	(Liability)		Technique	Unobservable Input	Range
	(In millions)
Basis contracts	$	(6)	Discounted cash flow	NYMEX Natural gas price forward curve	$	2.75		-	$	3.36
				Physical pricing point forward curves	$	2.44		-	$	3.21
				Credit risk		0.05	%	-		0.64	%
Oil 3-way collar contracts	$	104	Option model	NYMEX Oil price forward curve	$	81.80		-	$	88.71
				Oil price volatility curves		22.44	%	-		40.74	%
				Credit risk		0.02	%	-		12.60	%
Natural gas 3-way collar contracts	$	87	Option model	NYMEX Natural gas price forward curve	$	2.75		-	$	4.22
				Natural gas price volatility curves		25.31	%	-		60.79	%
				Credit risk		0.02	%	-		4.17	%

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

	June 30,		December 31,
	2012		2011
	(In millions)
5¾% Senior Notes due 2022	$	788	$	808
5⅝% Senior Notes due 2024		1,028		—
6⅝% Senior Subordinated Notes due 2014		—		329
6⅝% Senior Subordinated Notes due 2016		565		568
7⅛% Senior Subordinated Notes due 2018		636		635
6⅞% Senior Subordinated Notes due 2020		744		745