Fair Value Measurements - Changes in Level 3 Financial Assets (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Fixed Maturities And Equity Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance		$ 818	$ 1,198	$ 857	$ 1,190
Gains (losses) included in shareholders' net income:
GMIB fair value gain/(loss)		0	0	0	0
Other		15	2	28	14
Total gains (losses) included in shareholders' net income		15	2	28	14
Gains (losses) included in other comprehensive income		(19)	9	(17)	17
Gains (losses) required to adjust future policy benefits for settlement annuities	[1]	(4)	20	2	42
Purchases, issuances, settlements:
Purchases		100	53	111	77
Sales		(210)	(91)	(228)	(115)
Settlements		(4)	(46)	(7)	(107)
Total purchases, sales, settlements		(114)	(84)	(124)	(145)
Transfers into/(out of) Level 3:
Transfers into Level 3		0	30	1	154
Transfers out of Level 3		(30)	(53)	(81)	(150)
Total transfers into/(out of) Level 3		(30)	(23)	(80)	4
Ending Balance		666	1,122	666	1,122
Total gains (losses) included in income attributable to instruments held at the reporting date		0	1	0	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		970	815	953	751
Gains (losses) included in shareholders' net income:
GMIB fair value gain/(loss)		(94)	53	(67)	130
Other		1	3	0	2
Total gains (losses) included in shareholders' net income		(93)	56	(67)	132
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)	(8)	(19)	(20)
Total purchases, sales, settlements		(10)	(8)	(19)	(20)
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		867	863	867	863
Total gains (losses) included in income attributable to instruments held at the reporting date		$ (93)	$ 56	$ (67)	$ 132

[1] Amounts do not accrue to shareholders.