Fair Value Measurements - Changes in Level 3 Financial Assets (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 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		(18)	24
Total gains (losses) included in shareholders' net income		(18)	24
Gains (losses) included in other comprehensive income		(1)	(11)
Gains (losses) required to adjust future policy benefits for settlement annuities	[1]	29	(1)
Purchases, sales, and settlements:
Purchases		96	153
Sales		(140)	(230)
Settlements		(74)	(21)
Total purchases, sales, settlements		(118)	(98)
Transfers into/(out of) Level 3:
Transfers into Level 3		338	49
Transfers out of Level 3		(180)	(94)
Total transfers into/(out of) Level 3		158	(45)
Ending Balance		776	726
Total gains (losses) included in income attributable to instruments held at the reporting date		(18)	(6)
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)		(47)	(5)
Other		0	1
Total gains (losses) included in shareholders' net income		(47)	(4)
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		(61)	(42)
Total purchases, sales, settlements		(61)	(42)
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		799	907
Total gains (losses) included in income attributable to instruments held at the reporting date		$ (47)	$ (4)

[1] Amounts do not accrue to shareholders.