Derivative Financial Instruments - Volume and Fair Value Positions of Derivative Instruments (Details) $ in Millions	Sep. 30, 2019 USD ($) contract	Dec. 31, 2018 USD ($) contract
Derivatives, Fair Value
Total asset derivatives, Notional amount	$ 300	$ 292
Total liability derivatives, Notional amount	2,070	2,107
Total derivatives, Notional amount	$ 2,370	$ 2,399
Total asset derivatives, Number of contracts | contract	3,174	3,796
Total liability derivatives, Number of contracts | contract	3,756	3,266
Total derivatives, Number of contracts | contract	6,930	7,062
Total asset derivatives, Fair value, net	$ 110	$ 28
Total liability derivatives, Fair value, net	(458)	(227)
Total derivatives, Fair value, net	(348)	(199)
Asset derivatives, Gross asset	112	30
Asset derivatives, Gross liability	(2)	(2)
Liability derivatives, Gross asset	0	1
Liability derivatives, Gross liability	(458)	(228)
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	$ 298
Total asset derivatives, Number of contracts | contract	3,174
Total asset derivatives, Fair value, net	$ 110
Asset derivatives, Gross asset	112
Asset derivatives, Gross liability	(2)
Other | Derivatives designated as fair value accounting hedging instruments | Other assets
Derivatives, Fair Value
Total asset derivatives, Notional amount	2
Total asset derivatives, Fair value, net	0
Asset derivatives, Gross asset	0
Asset derivatives, Gross liability	0
Other | Derivatives not designated as accounting hedging instruments | Other assets
Derivatives, Fair Value
Total asset derivatives, Notional amount		2
Total asset derivatives, Fair value, net		0
Asset derivatives, Gross asset		0
Asset derivatives, Gross liability		0
Interest rate contracts, futures | Derivatives not designated as accounting hedging instruments | Other assets
Derivatives, Fair Value
Total asset derivatives, Notional amount		$ 0
Total asset derivatives, Number of contracts | contract		330
Total asset derivatives, Fair value, net		$ 0
Asset derivatives, Gross asset		0
Asset derivatives, Gross liability		0
Interest rate contracts, futures | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	$ 0
Total liability derivatives, Number of contracts | contract	723
Total liability derivatives, Fair value, net	$ 0
Liability derivatives, Gross asset	0
Liability derivatives, Gross liability	0
Interest rate cap agreements | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	22	6
Total asset derivatives, Fair value, net	0	0
Asset derivatives, Gross asset	0	0
Asset derivatives, Gross liability	0	0
Interest rate cap agreements | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	13	31
Total liability derivatives, Fair value, net	0	1
Liability derivatives, Gross asset	0	1
Liability derivatives, Gross liability	0	0
Options | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	$ 0	$ 0
Total asset derivatives, Number of contracts | contract	3,149	3,440
Total asset derivatives, Fair value, net	$ 96	$ 21
Asset derivatives, Gross asset	96	21
Asset derivatives, Gross liability	0	0
Options | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	$ 0	$ 0
Total liability derivatives, Number of contracts | contract	3,025	3,266
Total liability derivatives, Fair value, net	$ (34)	$ (5)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(34)	(5)
Equity and index contracts, futures | Derivatives not designated as accounting hedging instruments | Other assets
Derivatives, Fair Value
Total asset derivatives, Notional amount	$ 0	$ 0
Total asset derivatives, Number of contracts | contract	25	26
Total asset derivatives, Fair value, net	$ 0	$ 0
Asset derivatives, Gross asset	0	0
Asset derivatives, Gross liability	0	0
Equity and index contracts, futures | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	$ 0
Total liability derivatives, Number of contracts | contract	8
Total liability derivatives, Fair value, net	$ 0
Liability derivatives, Gross asset	0
Liability derivatives, Gross liability	0
Total return swap agreements - fixed income | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	7	7
Total asset derivatives, Fair value, net	0	0
Asset derivatives, Gross asset	0	0
Asset derivatives, Gross liability	0	0
Total return swap agreements - equity index | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	12	10
Total asset derivatives, Fair value, net	0	(1)
Asset derivatives, Gross asset	0	0
Asset derivatives, Gross liability	0	(1)
Foreign currency forwards | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	223	240
Total asset derivatives, Fair value, net	15	8
Asset derivatives, Gross asset	16	8
Asset derivatives, Gross liability	(1)	0
Foreign currency forwards | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	6
Total liability derivatives, Fair value, net	0
Liability derivatives, Gross asset	0
Liability derivatives, Gross liability	0
Guaranteed accumulation benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	161	169
Total liability derivatives, Fair value, net	(21)	(25)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(21)	(25)
Guaranteed withdrawal benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	205	210
Total liability derivatives, Fair value, net	(16)	(14)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(16)	(14)
Equity-indexed and forward starting options in life and annuity product contracts | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	1,680	1,696
Total liability derivatives, Fair value, net	(387)	(184)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(387)	(184)
Credit default swaps – buying protection | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	29	27
Total asset derivatives, Fair value, net	(1)	0
Asset derivatives, Gross asset	0	1
Asset derivatives, Gross liability	(1)	(1)
Credit default swaps – buying protection | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	5
Total liability derivatives, Fair value, net	0
Liability derivatives, Gross asset	0
Liability derivatives, Gross liability	0
Credit default swaps – selling protection | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	5
Total asset derivatives, Fair value, net	0
Asset derivatives, Gross asset	0
Asset derivatives, Gross liability	0
Credit default swaps – selling protection | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	0	1
Total liability derivatives, Fair value, net	0	0
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	$ 0	$ 0