Fair Value Measurement and Fair Value of Financial Instruments (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Trading Assets
Reconciliation of assets measured using significant unobservable inputs
Reconciliation of asset balance at fair value on a recurring basis using significant unobservable inputs, beginning of period	$ 273	$ 186	$ 271	$ 136
Total gains (losses) (realized/unrealized) included in income before taxes	35	(5)	36	42
Purchases/additions, assets		1	3	4
Settlements	(5)		(7)
Reconciliation of asset balance at fair value on a recurring basis using significant unobservable inputs, end of period	303	182	303	182
Changes in unrealized gains (losses) included in income before taxes for assets still held at end of period	35	(5)	36	42
Securities Available for Sale
Reconciliation of assets measured using significant unobservable inputs
Reconciliation of asset balance at fair value on a recurring basis using significant unobservable inputs, beginning of period	2,046	1,592	2,018	1,499
Total gains (losses) (realized/unrealized) included in other comprehensive income	7	18	15	37
Purchases/additions, assets	14	192	137	329
Sales				(14)
Settlements	(122)	(40)	(225)	(89)
Reconciliation of asset balance at fair value on a recurring basis using significant unobservable inputs, end of period	1,945	1,762	1,945	1,762
Other assets
Reconciliation of assets measured using significant unobservable inputs
Reconciliation of asset balance at fair value on a recurring basis using significant unobservable inputs, beginning of period	1	1	1
Total gains (losses) (realized/unrealized) included in income before taxes	1	1	1	1
Purchases/additions, assets				1
Reconciliation of asset balance at fair value on a recurring basis using significant unobservable inputs, end of period	2	2	2	2
Changes in unrealized gains (losses) included in income before taxes for assets still held at end of period	$ 1	$ 1	$ 1	$ 1