Fair Value (Details 9) (Non Recurring [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Held-for-investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	$ 383	$ 289	$ 370	$ 273
Estimated Fair Value After Measurement	379	245	379	245
Net Investment Gain (Losses)	(4)	(44)	9	(28)
Held-for-sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	184	71	213	72
Estimated Fair Value After Measurement	174	68	174	68
Net Investment Gain (Losses)	(10)	(3)	(39)	(4)
Mortgage loans, net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	567	360	583	345
Estimated Fair Value After Measurement	553	313	553	313
Net Investment Gain (Losses)	(14)	(47)	(30)	(32)
Other limited partnership interests [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	36	5	84	18
Estimated Fair Value After Measurement	27	3	61	13
Net Investment Gain (Losses)	(9)	(2)	(23)	(5)
Real estate joint ventures [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	0	0	15	0
Estimated Fair Value After Measurement	0	0	10	0
Net Investment Gain (Losses)	0	0	(5)	0
Goodwill [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	1,868	65	1,868	65
Estimated Fair Value After Measurement	0	0	0	0
Net Investment Gain (Losses)	$ (1,868)	$ (65)	$ (1,868)	$ (65)