Fair Value (Nonrecurring Fair Value Measurements) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Level 3 | Mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value After Measurement	$ 44	$ 106	$ 44	$ 106
Level 3 | Other limited partnership interests
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Value After Measurement	53	92	53	92
Nonrecurring | Mortgage loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gains (Losses)	0	4	(1)	3
Nonrecurring | Other limited partnership interests
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gains (Losses)	$ (8)	$ (14)	$ (27)	$ (51)