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
		Mar. 31, 2017	Mar. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ (780)	$ (885)
Gains (losses) included in shareholders' net income:
GMIB fair value gain/(loss)		11	(61)
Other		(4)	(5)
Total gains (losses) included in shareholders' net income		7	(66)
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, settlements:
Purchases		0	0
Sales		0	0
Settlements		12	10
Total purchases, sales, and settlements		12	10
Transfers into/(out of) Level 3:
Transfers into Level 3		0	0
Transfers out of Level 3		0	0
Transfers into/(out of) Level 3		0	0
Ending balance		(761)	(941)
Total gains (losses) included in income attributable to instruments held at the reporting date		$ 7	$ (66)

[1] Amounts do not accrue to shareholders.