Fair Value Measurements - Changes in Level 3 Financial Assets (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Fixed Maturities And Equity Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance		$ 666	$ 1,122	$ 857	$ 1,190
Gains (losses) included in shareholders' net income:
GMIB fair value gain/(loss)		0	0	0	0
Other		1	0	29	14
Total gains (losses) included in shareholders' net income		1	0	29	14
Gains (losses) included in other comprehensive income		(1)	(3)	(18)	14
Gains (losses) required to adjust future policy benefits for settlement annuities	[1]	4	(3)	6	39
Purchases, issuances, settlements:
Purchases		25	6	136	83
Sales		(1)	(2)	(229)	(117)
Settlements		(13)	(43)	(20)	(150)
Total purchases, sales, settlements		11	(39)	(113)	(184)
Transfers into/(out of) Level 3:
Transfers into Level 3		48	10	49	164
Transfers out of Level 3		(8)	(103)	(89)	(253)
Total transfers into/(out of) Level 3		40	(93)	(40)	(89)
Ending Balance		721	984	721	984
Total gains (losses) included in income attributable to instruments held at the reporting date		(1)	1	(1)	3
Derivative Financial Instruments, Assets [Member] | Guaranteed Minimum Income Benefit [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance		867	863	953	751
Gains (losses) included in shareholders' net income:
GMIB fair value gain/(loss)		104	33	37	163
Other		0	0	0	2
Total gains (losses) included in shareholders' net income		104	33	37	165
Gains (losses) included in other comprehensive income		0	0	0	0
Gains (losses) required to adjust future policy benefits for settlement annuities	[1]	0	0	0	0
Purchases, issuances, settlements:
Purchases		0	0	0	0
Sales		0	0	0	0
Settlements		(10)	(16)	(29)	(36)
Total purchases, sales, settlements		(10)	(16)	(29)	(36)
Transfers into/(out of) Level 3:
Transfers into Level 3		0	0	0	0
Transfers out of Level 3		0	0	0	0
Total transfers into/(out of) Level 3		0	0	0	0
Ending Balance		961	880	961	880
Total gains (losses) included in income attributable to instruments held at the reporting date		$ 104	$ 33	$ 37	$ 165

[1] Amounts do not accrue to shareholders.