Fair Value Measurements (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Fair value of warrants	$ 124
Underlying assets of funds, estimated liquidation period, years, maximum	17 years
Commitments to fund additional investments in nonmarketable equity securities	2		1
Federal Home Loan Bank stock	89		92
Federal Reserve Bank stock	85		85
Recurring [Member]
Fair value of warrants	3
Transfers into or out of Level 1 or Level 2 or Level 3	0		0
Total liabilities at fair value	497		499
Nonrecurring [Member]
Total liabilities at fair value	0		0
Estimated Fair Value [Member]
Carrying value of nonmarketable equity securities	22	[1]	27	[1]
Carrying Amount [Member]
Carrying value of nonmarketable equity securities	13	[1]	16	[1]
Carrying value of loan servicing rights	$ 2

[1] Included $2 million and $1 million of nonmarketable equity securities recorded at fair value on a nonrecurring basis at December 31, 2012 and 2011, respectively.