Fair Value (Details 9) (Non Recurring [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Held-for-investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	$ 166	$ 176
Estimated Fair Value After Measurement	167	184
Net Investment Gain (Losses)	1	8
Held-for-sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	320	43
Estimated Fair Value After Measurement	304	43
Net Investment Gain (Losses)	(16)	0
Mortgage loans, net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	486	219
Estimated Fair Value After Measurement	471	227
Net Investment Gain (Losses)	(15)	8
Other limited partnership interests [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	10	0
Estimated Fair Value After Measurement	7	0
Net Investment Gain (Losses)	(3)	0
Real estate joint ventures [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	5	0
Estimated Fair Value After Measurement	2	0
Net Investment Gain (Losses)	$ (3)	$ 0