Shareholders' Equity (Details) (USD $) Share data in Millions, unless otherwise specified	12 Months Ended				1 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Oct. 31, 2012 Open Market Share Repurchases	Jun. 30, 2011 Open Market Share Repurchases	May 31, 2010 Open Market Share Repurchases	Dec. 31, 2012 Open Market Share Repurchases	Dec. 31, 2011 Open Market Share Repurchases	Dec. 31, 2010 Open Market Share Repurchases	Dec. 31, 2012 Franchise Advisor Deferral Plan	Dec. 31, 2011 Franchise Advisor Deferral Plan	Dec. 31, 2010 Franchise Advisor Deferral Plan
Components of accumulated other comprehensive income (loss), net of tax
Net unrealized securities gains	$ 1,312,000,000	$ 883,000,000
Net unrealized derivatives losses	(2,000,000)	(11,000,000)	18,000,000	3,000,000
Foreign currency translation	(25,000,000)	(46,000,000)
Defined benefit plans	(91,000,000)	(75,000,000)	(24,000,000)	(20,000,000)
Total	1,194,000,000	751,000,000	650,000,000	305,000,000
Common Share Repurchases:
Maximum expenditure authorized for repurchase of common stock					2,000,000,000	2,000,000,000	1,500,000,000
Repurchase of common shares (in shares)								24.6	27.9	13.1	0.3	0.3	0.1
Repurchase of common shares								1,300,000,000	1,500,000,000	573,000,000	21,000,000	13,000,000	7,000,000
Remaining Balance under Stock Repurchase Program								2,100,000,000
Restricted shares forfeited, recorded as treasury shares	0.2	0.1	0.3
Number of shares reacquired through surrender of restricted shares	0.3	0.5	0.4
Value of shares reacquired through surrender of restricted shares	$ 18,000,000	$ 25,000,000	$ 17,000,000
Treasury shares reissued for restricted stock award grants (in shares)	1.8	1.7
Treasury shares reissued for restricted stock award grants and Franchise Advisor Deferral Plan (in shares)	1.8	1.7