Share-Based Incentive Compensation (details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012 years	Mar. 31, 2011	Dec. 31, 2011 years
Share-Based Incentive Compensation disclosure
Stock options vested at end of period, number (in shares)	12,819,392
Stock options vested at end of period, weighted average exercise price (per share)	$ 47.28
Stock options vested at end of period, weighted average contractual life remaining (in years)	5.1
Stock options vested at end of period, aggregate intrinsic value	$ 155
Stock options exercisable at end of period, number (in shares)	9,283,250
Stock options exercisable at end of period, weighted average exercise price (per share)	$ 43.82
Stock options exercisable at end of period, weighted average contractual life remaining (in years)	4.1
Stock options exercisable at end of period, aggregate intrinsic value	143
Total compensation cost recognized in earnings for all share-based incentive compensation awards	38	37
Tax benefits recognized in the consolidated statement of income related to compensation costs	13	13
Total unrecognized compensation cost related to all nonvested share-based incentive compensation awards	$ 185		$ 114
Weighted-average period of recognition for unrecognized compensation cost (in years)	2.2		1.7