Employee Benefit Plans (Stock-Based Compensation Expense) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Employee Benefit Plans [Abstract]
Stock options, expense	$ 16	$ 22	$ 20
Restricted stock awards, expense	51	41	46
Total stock-based compensation expense	67	63	66
Tax benefit recognized	(25)	(23)	(24)
Stock-based compensation expense, net of tax	$ 42	$ 40	$ 42