Fair Value (Nonrecurring Fair Value Measurements) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Level 3 [Member] | Mortgage loans, net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value After Measurement	$ 106	$ 232	$ 106	$ 232
Level 3 [Member] | Other limited partnership interests [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value After Measurement	92	70	92	70
Level 3 [Member] | Real Estate Joint Ventures [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value After Measurement	0	3	0	3
Nonrecurring [Member] | Mortgage loans, net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gains (Losses)	4	(4)	3	13
Nonrecurring [Member] | Other limited partnership interests [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gains (Losses)	(14)	0	(51)	(39)
Nonrecurring [Member] | Real Estate Joint Ventures [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gains (Losses)	$ (1)	$ 0	$ (1)	$ (2)