Fair Value Measurements - Changes in Level 3 Financial Assets (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Fixed Maturities And Equity Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance		$ 726	$ 857
Gains (losses) included in shareholders' net income:
GMIB fair value gain/(loss)		0	0
Other		(25)	13
Total gains (losses) included in shareholders' net income		(25)	13
Gains (losses) included in other comprehensive income		0	2
Gains (losses) required to adjust future policy benefits for settlement annuities	[1]	11	6
Purchases, sales, and settlements:
Purchases		24	11
Sales		0	(18)
Settlements		(11)	(3)
Total purchases, sales, settlements		13	(10)
Transfers into/(out of) Level 3:
Transfers into Level 3		128	1
Transfers out of Level 3		(61)	(51)
Total transfers into/(out of) Level 3		67	(50)
Ending Balance		792	818
Total gains (losses) included in income attributable to instruments held at the reporting date		(25)	0
Derivative Financial Instruments, Assets [Member] | Guaranteed Minimum Income Benefit [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance		907	953
Gains (losses) included in shareholders' net income:
GMIB fair value gain/(loss)		61	27
Other		(1)	(1)
Total gains (losses) included in shareholders' net income		60	26
Gains (losses) included in other comprehensive income		0	0
Gains (losses) required to adjust future policy benefits for settlement annuities	[1]	0	0
Purchases, sales, and settlements:
Purchases		0	0
Sales		0	0
Settlements		(10)	(9)
Total purchases, sales, settlements		(10)	(9)
Transfers into/(out of) Level 3:
Transfers into Level 3		0	0
Transfers out of Level 3		0	0
Total transfers into/(out of) Level 3		0	0
Ending Balance		957	970
Total gains (losses) included in income attributable to instruments held at the reporting date		$ 60	$ 26

[1] Amounts do not accrue to shareholders.