Investment Securities (Details Textual) (USD $)	6 Months Ended
	Jun. 30, 2012 Y CreditScore	Dec. 31, 2011 Y
Investment Securities (Additional Textual) [Abstract]
Minimum weighted average credit score of prime securities	725
Maximum loan-to-value of prime securities	80.00%
Available-for-sale agency mortgage-backed securities transferred to held-to-maturity	$ 11,700,000,000
Weighted-average maturity of the available-for-sale investment securities (in years)	4.5	5.2
Weighted-average yields of available-for-sale investment securities	3.29%	3.19%
Weighted-average maturity of the held-to-maturity investment securities (in years)	3.4	3.9
Weighted-average yields of held-to-maturity investment securities	2.16%	2.21%
Securities pledged	20,200,000,000	20,700,000,000
Securities pledged as collateral where counterparty has right to repledge or resell	6,700,000,000	7,000,000,000
Unpaid principal balance of investment securities with evidence of credit deterioration at acquisition	388,000,000	416,000,000
Fair value of investment securities with evidence of credit deterioration at acquisition	148,000,000	145,000,000
Non-agency [Member] | Residential [Member]
Investment Securities (Textual) [Abstract]
Unrealized Losses Total	$ 270,000,000