Debt and Equity Transactions (Unaudited) Interest, Dividends and Maturities (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Nov. 05, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Oct. 30, 2015
Capitalized Interest [Line Items]
Interest costs incurred		$ 217	$ 212	$ 642	$ 661
Common Stock, Value of Shares Authorized for Issue in Transaction				$ 1,000
Stock Issued During Period, Shares, New Issues				98,000,000
Shares Issued, Price Per Share		$ 10.35		$ 10.35
Proceeds from Issuance of Common Stock, Gross				$ 1,010
Proceeds from Issuance of Common Stock				999	$ 0
Fees and Commissions				$ 10
Entity Common Stock, Shares Outstanding						1,155,870,213
Dividends Payable, Date Declared				Sep. 30, 2015
Dividends declared per share of common stock		$ 0.05	$ 0.3125	$ 0.2605	$ 0.9375
Dividends Payable, Date to be Paid		Nov. 02, 2015
Dividends Payable, Date of Record		Oct. 15, 2015
Property, Plant, Equipment and Mining Development Costs, Net [Member]
Capitalized Interest [Line Items]
Interest costs capitalized		$ 42	$ 34	$ 134	$ 113
Oil and Gas Properties Not Subject to Amortization [Member]
Capitalized Interest [Line Items]
Interest costs capitalized		$ 12	$ 20	$ 50	$ 65
Subsequent Event [Member]
Capitalized Interest [Line Items]
Common Stock, Value of Shares Authorized for Issue in Transaction	$ 1,000
Stock Issued During Period, Shares, New Issues	34,100,000
Shares Issued, Price Per Share	$ 12.15
Proceeds from Issuance of Common Stock, Gross	$ 414
Proceeds from Issuance of Common Stock	410
Fees and Commissions	$ 4