Debt and Equity Transactions (Unaudited) Interest, Dividends and Maturities (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Capitalized Interest [Line Items]
Interest costs incurred	$ 225	$ 167	$ 449	$ 242
Dividends Payable, Date Declared	Jun. 25, 2014
Authorized Quarterly Rate Of Common Stock Dividend	$ 0.3125
Dividends Payable, Date to be Paid	Aug. 01, 2014
Dividends Payable, Date of Record	Jul. 15, 2014
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares		91
Property, Plant, Equipment and Mining Development Costs, Net [Member]
Capitalized Interest [Line Items]
Interest costs capitalized	39	27	79	45
Oil and Gas Properties Not Subject to Amortization [Member]
Capitalized Interest [Line Items]
Interest costs capitalized	$ 22	$ 8	$ 45	$ 8