Investments (Details Textuals 21) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Variable Interest Entity [Line Items]
Remaining years to repayment of long-term debt held by consolidated securitization entities	5 years
Consolidated Securitization Entities [Member]
Variable Interest Entity [Line Items]
Variable interest, maximum exposure to loss in consolidated securitization entities	$ 176		$ 172
Long-term debt held by consolidated securitization entities, percentage range minimum	2.25%
Long-term debt held by consolidated securitization entities, percentage range maximum	5.57%
Interest expense on long-term debt held by consolidated securitization entities	$ 43	$ 92