Fair Value Measurements - Changes in Level 3 Financial Liabilities (Details) - Derivative Financial Instruments, Liabilities [Member] - Guaranteed Minimum Income Benefit [Member] - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ (941)	$ (948)	$ (885)	$ (929)
Gains (losses) included in shareholders' net income:
GMIB fair value gain/(loss)		(32)	94	(93)	67
Other		12	3	7	2
Total gains (losses) included in shareholders' net income		(20)	97	(86)	69
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, sales, settlements:
Purchases		0	0	0	0
Sales		0	0	0	0
Settlements		14	10	24	19
Total purchases, sales, and settlements		14	10	24	19
Transfers into/(out of) Level 3:
Transfers into Level 3		0	0	0	0
Transfers out of Level 3		0	0	0	0
Transfers into/(out of) Level 3		0	0	0	0
Ending balance		(947)	(841)	(947)	(841)
Total gains (losses) included in income attributable to instruments held at the reporting date		$ (20)	$ 97	$ (86)	$ 69

[1] Amounts do not accrue to shareholders.