Subsequent Events (Details) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 23, 2015	Jan. 21, 2015	Jan. 27, 2015	Jan. 30, 2015	Dec. 19, 2014
Subsequent Event [Line Items]
Capitalized costs incurred	$ 7,221,000,000	$ 2,023,000,000	$ 1,911,000,000
Bridge Loan [Member]
Subsequent Event [Line Items]
Bridge loan	4,500,000,000							4,500,000,000
Debt instrument, term	364 days
Subsequent Event [Member]
Subsequent Event [Line Items]
Proceeds from issuance of shares					2,300,000,000
Share price					$ 23.00
Depositary shares conversion rate					0.05
Proceeds from issuance of senior notes				2,200,000,000
Subsequent Event [Member] | 3.300% Senior Notes Due 2018 [Member]
Subsequent Event [Line Items]
Senior notes				350,000,000
Stated interest rate				3.30%
Discount on senior notes				99.949%
Subsequent Event [Member] | 4.050% Senior Notes Due 2020 [Member]
Subsequent Event [Line Items]
Senior notes				850,000,000
Stated interest rate				4.05%
Discount on senior notes				99.897%
Subsequent Event [Member] | 4.950% Senior Notes Due 2025 [Member]
Subsequent Event [Line Items]
Senior notes				1,000,000,000
Stated interest rate				4.95%
Discount on senior notes				99.782%
Subsequent Event [Member] | Statoil Property [Member]
Subsequent Event [Line Items]
Area of property						30,000
Interest in property						20.00%
Acquisition price						365,000,000
Subsequent Event [Member] | WPX Property [Member]
Subsequent Event [Line Items]
Area of property							46,700
Acquisition price							288,000,000
Subsequent Event [Member] | Common Stock [Member]
Subsequent Event [Line Items]
Shares issued					30,000,000
Proceeds from issuance of shares					669,000,000
Subsequent Event [Member] | Depositary Shares [Member]
Subsequent Event [Line Items]
Shares issued					34,500,000
Proceeds from issuance of shares					$ 1,700,000,000
Preferred stock, liquidation preference per share					$ 50
Subsequent Event [Member] | Preferred Stock [Member]
Subsequent Event [Line Items]
Preferred stock dividend rate					6.25%
Preferred stock, liquidation preference per share					$ 1,000