Derivative Instruments - Summary of Notional and Fair Value of Derivative Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Total derivative assets, including embedded derivatives, fair value	$ 2,087	$ 1,510
Total derivative liabilities, including embedded derivatives, fair value	6,285	5,329
Derivatives designated as hedges
Derivative [Line Items]
Derivative assets, fair value	1	11
Derivative liabilities, fair value	32	18
Derivatives designated as hedges | Foreign currency swaps
Derivative [Line Items]
Notional Amount	592	289
Derivative assets, fair value	1	11
Derivative liabilities, fair value	32	4
Derivatives designated as hedges | Interest rate swaps
Derivative [Line Items]
Notional Amount	302	302
Derivative assets, fair value	0	0
Derivative liabilities, fair value	0	14
Derivatives not designated as hedges
Derivative [Line Items]
Total derivative assets, including embedded derivatives, fair value	2,086	1,499
Total derivative liabilities, including embedded derivatives, fair value	6,253	5,311
Derivatives not designated as hedges | Foreign currency swaps
Derivative [Line Items]
Notional Amount	42	43
Derivative assets, fair value	3	5
Derivative liabilities, fair value	2	0
Derivatives not designated as hedges | Interest rate swaps
Derivative [Line Items]
Notional Amount	457	568
Derivative assets, fair value	1	1
Derivative liabilities, fair value	2	5
Derivatives not designated as hedges | Equity options
Derivative [Line Items]
Notional Amount	29,649	26,822
Derivative assets, fair value	1,775	1,336
Derivative liabilities, fair value	10	0
Derivatives not designated as hedges | Futures
Derivative [Line Items]
Notional Amount	12	0
Derivative assets, fair value	5	9
Derivative liabilities, fair value	1	0
Derivatives not designated as hedges | Total return swaps
Derivative [Line Items]
Notional Amount	110	41
Derivative assets, fair value	2	2
Derivative liabilities, fair value	0	0
Derivatives not designated as hedges | Credit default swaps
Derivative [Line Items]
Notional Amount	10	10
Derivative assets, fair value	0	0
Derivative liabilities, fair value	6	7
Derivatives not designated as hedges | Variance swaps
Derivative [Line Items]
Notional Amount	0	0
Derivative assets, fair value	1	0
Derivative liabilities, fair value	0	0
Derivatives not designated as hedges | Foreign currency forwards
Derivative [Line Items]
Notional Amount	790	805
Derivative assets, fair value	20	6
Derivative liabilities, fair value	10	10
Derivatives not designated as hedges | Embedded derivatives | Funds withheld
Derivative [Line Items]
Notional Amount	0	0
Embedded derivative assets, fair value	279	140
Embedded derivative liabilities, fair value	15	6
Derivatives not designated as hedges | Embedded derivatives | Interest sensitive contract liabilities
Derivative [Line Items]
Notional Amount	0	0
Embedded derivative assets, fair value	0	0
Embedded derivative liabilities, fair value	$ 6,207	$ 5,283