Earnings Per Share and Equity - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Statement Of Equity Line Item [Line Items]
Stock options not included in the calculation of diluted common shares outstanding	13,000,000	15,000,000
Treasury Stock, Shares held	35,000,000		35,000,000
Treasury Stock, Value	$ 2,327		$ 2,327
Equity units issued [Member]
Statement Of Equity Line Item [Line Items]
Stock options not included in the calculation of diluted common shares outstanding	4,000,000	1,000,000
Employee Stock Option [Member]
Statement Of Equity Line Item [Line Items]
Stock options not included in the calculation of diluted common shares outstanding	16,000,000	20,000,000