Fair Value (Details 9) (Non Recurring [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Held-for-investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	$ 197	$ 174	$ 197	$ 165
Estimated Fair Value After Measurement	209	182	210	182
Net Investment Gain (Losses)	12	8	13	17
Held-for-sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	254	47	270	48
Estimated Fair Value After Measurement	239	47	239	47
Net Investment Gain (Losses)	(15)	0	(31)	(1)
Mortgage loans, net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	451	221	467	213
Estimated Fair Value After Measurement	448	229	449	229
Net Investment Gain (Losses)	(3)	8	(18)	16
Other limited partnership interests [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	38	13	48	13
Estimated Fair Value After Measurement	27	10	34	10
Net Investment Gain (Losses)	(11)	(3)	(14)	(3)
Real estate joint ventures [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value Prior to Measurement	10	0	15	0
Estimated Fair Value After Measurement	8	0	10	0
Net Investment Gain (Losses)	$ (2)	$ 0	$ (5)	$ 0