Share-Based Incentive Compensation (details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Share-Based Incentive Compensation disclosure
Stock options vested at end of period, number (in shares)	8,470,852		8,470,852
Stock options vested at end of period, weighted average exercise price (per share)	$ 52.85		$ 52.85
Stock options vested at end of period, weighted average contractual life remaining (in years)			5 years 8 months 12 days
Stock options vested at end of period, aggregate intrinsic value	$ 270		$ 270
Stock options exercisable at end of period, number (in shares)	5,594,322		5,594,322
Stock options exercisable at end of period, weighted average exercise price (per share)	$ 47.06		$ 47.06
Stock options exercisable at end of period, weighted average contractual life remaining (in years)			4 years 4 months 24 days
Stock options exercisable at end of period, aggregate intrinsic value	211		211
Total compensation cost recognized in earnings for all share-based incentive compensation awards	29	26	99	92
Tax benefits recognized in earnings related to compensation costs	10	9	34	32
Total unrecognized compensation cost related to all nonvested share-based incentive compensation awards	$ 142		$ 142		$ 112
Weighted-average period of recognition for unrecognized compensation cost (in years)			1 year 9 months 18 days		1 year 8 months 12 days