Business Changes and Developments - Stock Dividends and Repurchases (Details) (USD $) In Billions, except Per Share data, unless otherwise specified	2 Months Ended	3 Months Ended
	May 04, 2012 Common stock	Mar. 13, 2012 Common stock	Mar. 31, 2012 Approved Repurchase Program Period Start in 2012 [Member]	Mar. 31, 2012 Repurchase Program Authorized Period of 2012 [Member]	Mar. 31, 2012 Approved Repurchase Program Period Start in 2011 [Member]
Changes in common stock dividend
Common Stock Quarterly Dividend Rate per Share	$ 0.30	$ 0.25
Stock repurchases
Stock Repurchase Program Amount Authorized for Repurchase of Common Equity			$ 15.0	$ 12.0	$ 15.0