Share-Based Incentive Compensation (details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Share-Based Incentive Compensation disclosure
Stock options vested at end of period, number (in shares)	8,658,131		8,658,131
Stock options vested at end of period, weighted average exercise price (per share)	$ 52.58		$ 52.58
Stock options vested at end of period, weighted average contractual life remaining (in years)			5 years 10 months 24 days
Stock options vested at end of period, aggregate intrinsic value	$ 237		$ 237
Stock options exercisable at end of period, number (in shares)	5,743,635		5,743,635
Stock options exercisable at end of period, weighted average exercise price (per share)	$ 46.80		$ 46.80
Stock options exercisable at end of period, weighted average contractual life remaining (in years)			4 years 7 months 6 days
Stock options exercisable at end of period, aggregate intrinsic value	190		190
Total compensation cost recognized in earnings for all share-based incentive compensation awards	29	28	70	66
Tax benefits recognized in earnings related to compensation costs	10	10	24	23
Total unrecognized compensation cost related to all nonvested share-based incentive compensation awards	$ 166		$ 166		$ 112
Weighted-average period of recognition for unrecognized compensation cost (in years)			2 years 0 months 0 days		1 year 8 months 12 days