Stock-Based Compensation Stock-Based Compensation, Stock Appreciation Rights, Performance Share Awards and Market Stock Units(Details) (USD $) In Millions, except Per Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Stock appreciation rights
Stock-Based Compensation Arrangement by Stock-based Payment Award
Cash paid to settle awards	$ 22	$ 32
Exercised stock appreciation rights (shares)	0.8	1.4
Accrued stock appreciation rights	$ 53		$ 76
Performance share awards
Stock-Based Compensation Arrangement by Stock-based Payment Award
Awards granted (shares)	0.2
Weighted average grant date fair value (dollars per share)	$ 53.89
Market stock units
Stock-Based Compensation Arrangement by Stock-based Payment Award
Awards granted (shares)	0.5
Weighted average grant date fair value (dollars per share)	$ 59.83