Fair Value Measurements (Details 3) (Nonrecurring [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Impaired Loans Fair Value Disclosure	$ 81	$ 149
Loans Held-for-sale, Fair Value Disclosure	15	15
Accrued Income and Other Assets Fair Value Disclosure	42	44
Total assets on a recurring basis at fair value	138	208
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Impaired Loans Fair Value Disclosure
Loans Held-for-sale, Fair Value Disclosure
Accrued Income and Other Assets Fair Value Disclosure
Total assets on a recurring basis at fair value
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Impaired Loans Fair Value Disclosure
Loans Held-for-sale, Fair Value Disclosure
Accrued Income and Other Assets Fair Value Disclosure	17	19
Total assets on a recurring basis at fair value	17	19
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Impaired Loans Fair Value Disclosure	81	149
Loans Held-for-sale, Fair Value Disclosure	15	15
Accrued Income and Other Assets Fair Value Disclosure	25	25
Total assets on a recurring basis at fair value	$ 121	$ 189