Investments - Available-for-Sale Securities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	$ 40,078	$ 35,603
Gross Unrealized Gains, fixed maturities, available-for-sale	2,125	703
Gross Unrealized Losses, fixed maturities, available-for-sale	(55)	(654)
Total fixed maturities	42,148	35,652
Non-Credit OTTI	(4)	(5)
Amortized Cost
One year or less	1,082	999
Over one year through five years	7,200	5,786
Over five years through ten years	7,395	6,611
Over ten years	11,769	12,629
Subtotal	27,446	26,025
Mortgage-backed and asset-backed securities	12,632	9,578
Fair Value
One year or less	1,090	1,002
Over one year through five years	7,401	5,791
Over five years through ten years	7,803	6,495
Over ten years	12,988	12,820
Subtotal	29,282	26,108
Mortgage-backed and asset-backed securities	12,866	9,544
ABS
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	1,461	1,272
Gross Unrealized Gains, fixed maturities, available-for-sale	18	5
Gross Unrealized Losses, fixed maturities, available-for-sale	(3)	(1)
Total fixed maturities	1,476	1,276
Non-Credit OTTI	0	0
Collateralized loan obligations (CLOs)
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	2,186	1,455
Gross Unrealized Gains, fixed maturities, available-for-sale	5	2
Gross Unrealized Losses, fixed maturities, available-for-sale	(8)	(20)
Total fixed maturities	2,183	1,437
Non-Credit OTTI	0	0
CMBS
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	4,210	3,581
Gross Unrealized Gains, fixed maturities, available-for-sale	141	35
Gross Unrealized Losses, fixed maturities, available-for-sale	(13)	(64)
Total fixed maturities	4,338	3,552
Non-Credit OTTI	(4)	(5)
Corporate
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	16,435	13,696
Gross Unrealized Gains, fixed maturities, available-for-sale	986	148
Gross Unrealized Losses, fixed maturities, available-for-sale	(25)	(446)
Total fixed maturities	17,396	13,398
Non-Credit OTTI	0	0
Foreign government/government agencies
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	1,057	866
Gross Unrealized Gains, fixed maturities, available-for-sale	66	7
Gross Unrealized Losses, fixed maturities, available-for-sale	0	(26)
Total fixed maturities	1,123	847
Non-Credit OTTI	0	0
Municipal
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	8,763	9,972
Gross Unrealized Gains, fixed maturities, available-for-sale	737	421
Gross Unrealized Losses, fixed maturities, available-for-sale	(2)	(47)
Total fixed maturities	9,498	10,346
Non-Credit OTTI	0	0
Residential mortgage-backed securities (RMBS)
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	4,775	3,270
Gross Unrealized Gains, fixed maturities, available-for-sale	97	44
Gross Unrealized Losses, fixed maturities, available-for-sale	(3)	(35)
Total fixed maturities	4,869	3,279
Non-Credit OTTI	0	0
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	1,191	1,491
Gross Unrealized Gains, fixed maturities, available-for-sale	75	41
Gross Unrealized Losses, fixed maturities, available-for-sale	(1)	(15)
Total fixed maturities	1,265	1,517
Non-Credit OTTI	$ 0	$ 0