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, 2012	Dec. 31, 2011	Jun. 30, 2012 Level2 [Member]	Jun. 30, 2011 Level2 [Member]	Jun. 30, 2012 Fair Value Measurements Nonrecurring [Member]	Jun. 30, 2011 Fair Value Measurements Nonrecurring [Member]	Jun. 30, 2012 Fair Value Measurements Nonrecurring [Member]	Jun. 30, 2011 Fair Value Measurements Nonrecurring [Member]	Jun. 30, 2012 Fair Value Measurements Nonrecurring [Member] Level1 [Member]	Jun. 30, 2011 Fair Value Measurements Nonrecurring [Member] Level1 [Member]	Jun. 30, 2012 Fair Value Measurements Nonrecurring [Member] Level2 [Member]	Jun. 30, 2011 Fair Value Measurements Nonrecurring [Member] Level2 [Member]	Jun. 30, 2012 Fair Value Measurements Nonrecurring [Member] Level3 [Member]	Jun. 30, 2011 Fair Value Measurements Nonrecurring [Member] Level3 [Member]
Loans
Impaired loans	$ 569	$ 572			$ 114	$ 254	$ 114	$ 254					$ 114	$ 254
Unrealized holding loss on impaired loans					(33)	(5)	(36)	(51)
Other Assets
Other real estate owned at fair value					66	103	66	103					66	103
OREO					(9)	(9)	(17)	(19)
Private equity investments							(2)
Financial instruments owned at fair value, total					180	357	180	357					180	357
Total					$ (42)	$ (14)	$ (55)	$ (70)