Fair Value Measurements - Changes in Level 3 Financial Assets (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Fixed Maturities And Equity Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance		$ 857	$ 1,190
Gains (losses) included in shareholders' net income:
GMIB fair value gain/(loss)		0	0
Other		24	15
Total gains (losses) included in shareholders' net income		24	15
Gains (losses) included in other comprehensive income		(11)	14
Gains (losses) required to adjust future policy benefits for settlement annuities	[1]	(1)	55
Purchases, sales, settlements:
Purchases		153	101
Sales		(230)	(202)
Settlements		(21)	(156)
Total purchases, sales, settlements		(98)	(257)
Transfers into/(out of) Level 3:
Transfers into Level 3		49	165
Transfers out of Level 3		(94)	(325)
Total transfers into/(out of) Level 3		(45)	(160)
Ending Balance		726	857
Total gains (losses) included in income attributable to instruments held at the reporting date		(6)	2
Derivative Financial Instruments, Assets [Member] | Guaranteed Minimum Income Benefit [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance		953	751
Gains (losses) included in shareholders' net income:
GMIB fair value gain/(loss)		(5)	251
Other		1	(1)
Total gains (losses) included in shareholders' net income		(4)	250
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, settlements:
Purchases		0	0
Sales		0	0
Settlements		(42)	(48)
Total purchases, sales, settlements		(42)	(48)
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		907	953
Total gains (losses) included in income attributable to instruments held at the reporting date		$ (4)	$ 250

[1] Amounts do not accrue to shareholders.