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		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ (947)	$ (841)	$ (885)	$ (929)
Gains (losses) included in shareholders' net income:
GMIB fair value gain/(loss)		22	(104)	(71)	(37)
Other		(6)	0	1	2
Total gains (losses) included in shareholders' net income		16	(104)	(70)	(35)
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		23	10	47	29
Total purchases, sales, and settlements		23	10	47	29
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		(908)	(935)	(908)	(935)
Total gains (losses) included in income attributable to instruments held at the reporting date		$ 16	$ (104)	$ (70)	$ (35)

[1] Amounts do not accrue to shareholders.