Derivative Financial Instruments and Off-balance sheet Financial Instruments - Volume and fair value positions of derivative instruments (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) contract	Dec. 31, 2018 USD ($) contract	Dec. 31, 2017 contract
Derivatives, Fair Value
Assumed recoveries under sale of credit protection	$ 0
Securities pledged in the form of margin deposits	6,000,000
Total asset derivatives, Notional amount	10,000,000	$ 292,000,000
Total liability derivatives, Notional amount	2,375,000,000	2,107,000,000
Total derivatives, Notional amount	$ 2,385,000,000	$ 2,399,000,000
Total asset derivatives, Number of contracts | contract	3,484	3,796
Total liability derivatives, Number of contracts | contract	3,108	3,266
Total derivatives, Number of contracts | contract	6,592	7,062
Total asset derivatives, Fair value, net	$ 124,000,000	$ 28,000,000
Asset derivatives, Gross asset	124,000,000	30,000,000
Asset derivatives, Gross liability	0	(2,000,000)
Derivative liabilities net amount on balance sheet	(482,000,000)	(227,000,000)
Total derivatives, Fair value, net	(358,000,000)	(199,000,000)
Liability derivatives, Gross asset	10,000,000	1,000,000
Liability derivatives, Gross liability	(492,000,000)	(228,000,000)
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	$ 8,000,000
Total asset derivatives, Number of contracts | contract	3,484
Total asset derivatives, Fair value, net	$ 124,000,000
Asset derivatives, Gross asset	124,000,000
Asset derivatives, Gross liability	0
Interest rate cap agreements | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount		31,000,000
Derivative liabilities net amount on balance sheet		1,000,000
Liability derivatives, Gross asset		1,000,000
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		6,000,000
Total asset derivatives, Fair value, net		0
Asset derivatives, Gross asset		0
Asset derivatives, Gross liability		0
Interest rate cap agreements | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	34,000,000
Derivative liabilities net amount on balance sheet	0
Liability derivatives, Gross asset	0
Liability derivatives, Gross liability	0
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	476	330
Total asset derivatives, Fair value, net	$ 0	$ 0
Asset derivatives, Gross asset	0	0
Asset derivatives, Gross liability	0	0
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	263
Derivative liabilities net amount on balance sheet	$ 0
Liability derivatives, Gross asset	0
Liability derivatives, Gross liability	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	2,981	3,440
Total asset derivatives, Fair value, net	$ 124,000,000	$ 21,000,000
Asset derivatives, Gross asset	124,000,000	21,000,000
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
Total liability derivatives, Number of contracts | contract	2,844
Derivative liabilities net amount on balance sheet	$ (60,000,000)
Liability derivatives, Gross asset	0
Liability derivatives, Gross liability	(60,000,000)
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	27	26
Total asset derivatives, Fair value, net	$ 0	$ 0
Asset derivatives, Gross asset	0	0
Asset derivatives, Gross liability	0	0
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	1
Derivative liabilities net amount on balance sheet	$ 0
Liability derivatives, Gross asset	0
Liability derivatives, Gross liability	0
Total return swaps - fixed income | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	7,000,000	7,000,000
Total asset derivatives, Fair value, net	0	0
Asset derivatives, Gross asset	0	0
Asset derivatives, Gross liability	0	0
Total return swaps - fixed income | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	10,000,000
Derivative liabilities net amount on balance sheet	0
Liability derivatives, Gross asset	0
Liability derivatives, Gross liability	0
Total return swaps - equity index | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount		10,000,000
Total asset derivatives, Fair value, net		(1,000,000)
Asset derivatives, Gross asset		0
Asset derivatives, Gross liability		(1,000,000)
Total return swaps - equity index | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	14,000,000
Derivative liabilities net amount on balance sheet	1,000,000
Liability derivatives, Gross asset	1,000,000
Liability derivatives, Gross liability	0
Foreign currency forwards | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount		240,000,000
Total asset derivatives, Fair value, net		8,000,000
Asset derivatives, Gross asset		8,000,000
Asset derivatives, Gross liability		0
Foreign currency forwards | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	242,000,000
Derivative liabilities net amount on balance sheet	6,000,000
Liability derivatives, Gross asset	9,000,000
Liability derivatives, Gross liability	(3,000,000)
Credit default swaps - buying protection | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	1,000,000	27,000,000
Total asset derivatives, Fair value, net	0	0
Asset derivatives, Gross asset	0	1,000,000
Asset derivatives, Gross liability	0	(1,000,000)
Credit default swaps - buying protection | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	26,000,000
Derivative liabilities net amount on balance sheet	(2,000,000)
Liability derivatives, Gross asset	0
Liability derivatives, Gross liability	(2,000,000)
Credit default swaps – selling protection | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	5,000,000	1,000,000
Derivative liabilities net amount on balance sheet	0	0
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	0	0
Other | Derivatives designated as accounting hedging instruments | Other assets
Derivatives, Fair Value
Total asset derivatives, Notional amount	2,000,000
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		2,000,000
Total asset derivatives, Fair value, net		0
Asset derivatives, Gross asset		0
Asset derivatives, Gross liability		0
Options | 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		3,266
Derivative liabilities net amount on balance sheet		$ (5,000,000)
Liability derivatives, Gross asset		0
Liability derivatives, Gross liability		(5,000,000)
Guaranteed accumulation benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	161,000,000	169,000,000
Derivative liabilities net amount on balance sheet	(18,000,000)	(25,000,000)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(18,000,000)	(25,000,000)
Guaranteed withdrawal benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	205,000,000	210,000,000
Derivative liabilities net amount on balance sheet	(14,000,000)	(14,000,000)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	(14,000,000)	(14,000,000)
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	1,678,000,000	1,696,000,000
Derivative liabilities net amount on balance sheet	(395,000,000)	(184,000,000)
Liability derivatives, Gross asset	0	0
Liability derivatives, Gross liability	$ (395,000,000)	$ (184,000,000)
Fair Value Hedging | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total derivatives, Number of contracts | contract	1	0	0
Cash Flow Hedging | Derivatives designated as accounting hedging instruments
Derivatives, Fair Value
Total derivatives, Number of contracts | contract	0	1	1