Mortgage Servicing Assets (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2011
Mortgage Servicing Assets (Textual) [Abstract]
Prepayment speed, rate, min	0.00%	0.00%
Prepayment speed, rate, max	25.00%	25.00%
Expected credit losses, rate, min	2.00%	2.00%
Expected credit losses, rate, max	3.00%	3.00%
Residual cash flows discount rate, min	7.00%	7.00%
Residual cash flows discount rate, max	15.00%	15.00%
Interest rate for mortgage funds, min	0.00%	0.00%
Interest rate for mortgage funds, max	4.57%	4.57%
Increase (decrease) in value assigned to escrow deposits	(1.00%)
Increase (decrease) in assumed default rate of commercial mortgage loans	1.00%
Increase (decrease) in the fair value of mortgage servicing assets	$ (25,000,000)
Increase (decrease) in the fair value of mortgage servicing assets due to change in the assumed default rate of commercial mortgage loans	(2,000,000)
Contractual fee income from servicing commercial mortgage loans	96,000,000	72,000,000
Escrow Deposit			$ 1,500,000,000