Derivative Instruments - Summary of Notional and Fair Value of Derivative Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Total derivative assets	$ 3,504	$ 990
Total derivative liabilities	10,009	8,053
Derivatives designated as hedges
Derivative [Line Items]
Derivative assets, fair value	124	83
Derivative liabilities, fair value	49	56
Derivatives designated as hedges | Foreign currency swaps
Derivative [Line Items]
Notional Amount	2,487	2,041
Derivative assets, fair value	124	83
Derivative liabilities, fair value	48	55
Derivatives designated as hedges | Foreign currency forwards
Derivative [Line Items]
Notional Amount	246	85
Derivative assets, fair value	0	0
Derivative liabilities, fair value	1	1
Derivatives not designated as hedges
Derivative [Line Items]
Total derivative assets	3,380	907
Total derivative liabilities	9,960	7,997
Derivatives not designated as hedges | Foreign currency swaps
Derivative [Line Items]
Notional Amount	38	38
Derivative assets, fair value	3	3
Derivative liabilities, fair value	1	2
Derivatives not designated as hedges | Interest rate swaps
Derivative [Line Items]
Notional Amount	310	326
Derivative assets, fair value	0	0
Derivative liabilities, fair value	1	1
Derivatives not designated as hedges | Equity options
Derivative [Line Items]
Notional Amount	49,351	49,821
Derivative assets, fair value	2,153	942
Derivative liabilities, fair value	19	11
Derivatives not designated as hedges | Futures
Derivative [Line Items]
Notional Amount	7	4
Derivative assets, fair value	6	9
Derivative liabilities, fair value	1	3
Derivatives not designated as hedges | Total return swaps
Derivative [Line Items]
Notional Amount	60	62
Derivative assets, fair value	0	0
Derivative liabilities, fair value	0	3
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	4	4
Derivatives not designated as hedges | Foreign currency forwards
Derivative [Line Items]
Notional Amount	2,645	646
Derivative assets, fair value	13	6
Derivative liabilities, fair value	5	5
Derivatives not designated as hedges | Embedded derivatives | Funds withheld
Derivative [Line Items]
Notional Amount	0	0
Embedded derivative assets, fair value		(53)
Embedded derivative liabilities, fair value		(1)
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	9,905	7,969
Consolidated Entity Excluding Variable Interest Entities (VIE)
Derivative [Line Items]
Funds withheld liability	759	721
Derivative liabilities, fair value	80	$ 85
Consolidated Entity Excluding Variable Interest Entities (VIE) | Derivatives not designated as hedges | Embedded derivatives | Funds withheld
Derivative [Line Items]
Funds withheld at interest	1,205
Funds withheld liability	$ 24