Level 4~Investments - Available-for-Sale Securities (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	$ 35,330	$ 35,612
Gross Unrealized Gains, fixed maturities, available-for-sale	987	1,466
Gross Unrealized Losses, fixed maturities, available-for-sale	(393)	(114)
Total fixed maturities	35,924	36,964
Non-Credit OTTI	(5)	(5)
Equity securities, available-for-sale, Cost or Amortized Cost	0	907
Available-for-sale Securities, Equity Securities	0	1,012
Available-for-sale, Cost or Amortized Cost	35,330	36,519
Available-for-sale, Gross Unrealized Gains	987	1,587
Available-for-sale, Gross Unrealized Losses	(393)	(130)
Available-for-sale, Fair Value	35,924	37,976
Amortized Cost
One year or less	1,425	1,507
Over one year through five years	5,361	5,007
Over five years through ten years	6,499	6,505
Over ten years	13,591	13,928
Subtotal	26,876	26,947
Mortgage-backed and asset-backed securities	8,454	8,665
Fair Value
One year or less	1,430	1,513
Over one year through five years	5,414	5,119
Over five years through ten years	6,525	6,700
Over ten years	14,103	14,866
Subtotal	27,472	28,198
Mortgage-backed and asset-backed securities	8,452	8,766
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Non-Credit OTTI		0
Equity securities, available-for-sale, Cost or Amortized Cost		907
Gross Unrealized Gains, fixed maturities, available-for-sale		121
Gross Unrealized Losses Gains, fixed maturities, available-for-sale		(16)
Available-for-sale Securities, Equity Securities		1,012
ABS
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	911	1,119
Gross Unrealized Gains, fixed maturities, available-for-sale	6	9
Gross Unrealized Losses, fixed maturities, available-for-sale	(6)	(2)
Total fixed maturities	911	1,126
Non-Credit OTTI	0	0
CDOs
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	1,145	1,257
Gross Unrealized Gains, fixed maturities, available-for-sale	1	3
Gross Unrealized Losses, fixed maturities, available-for-sale	(2)	0
Total fixed maturities	1,144	1,260
Non-Credit OTTI	0	0
CMBS
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	3,334	3,304
Gross Unrealized Gains, fixed maturities, available-for-sale	34	58
Gross Unrealized Losses, fixed maturities, available-for-sale	(57)	(26)
Total fixed maturities	3,311	3,336
Non-Credit OTTI	(5)	(5)
Corporate
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	12,550	12,370
Gross Unrealized Gains, fixed maturities, available-for-sale	294	490
Gross Unrealized Losses, fixed maturities, available-for-sale	(210)	(56)
Total fixed maturities	12,634	12,804
Non-Credit OTTI	0	0
Foreign government/government agencies
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	1,076	1,071
Gross Unrealized Gains, fixed maturities, available-for-sale	22	43
Gross Unrealized Losses, fixed maturities, available-for-sale	(16)	(4)
Total fixed maturities	1,082	1,110
Non-Credit OTTI	0	0
Municipal
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	11,052	11,743
Gross Unrealized Gains, fixed maturities, available-for-sale	541	754
Gross Unrealized Losses, fixed maturities, available-for-sale	(49)	(12)
Total fixed maturities	11,544	12,485
Non-Credit OTTI	0	0
RMBS
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	3,064	2,985
Gross Unrealized Gains, fixed maturities, available-for-sale	54	63
Gross Unrealized Losses, fixed maturities, available-for-sale	(32)	(4)
Total fixed maturities	3,086	3,044
Non-Credit OTTI	0	0
U.S. Treasuries
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, available-for-sale, at fair value, amortized cost	2,198	1,763
Gross Unrealized Gains, fixed maturities, available-for-sale	35	46
Gross Unrealized Losses, fixed maturities, available-for-sale	(21)	(10)
Total fixed maturities	2,212	1,799
Non-Credit OTTI	$ 0	$ 0