Investments (Narrative) (Details) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Gain (Loss) on Securities [Line Items]
Non-income producing fixed maturity securities	$ 1,000,000	$ 1,000,000
Investments that exceed ten percent of stockholders' equity	0	0
Mortgage loan losses due to changes in expected credit losses	21,000,000	0	$ 0
Limited partnership investments	1,619,000,000	1,752,000,000
Undistributed earnings of limited partnership investments	$ 235,000,000	$ 229,000,000
Percentage of limited partnerships reported on a current basis	49.00%
Percentage of limited partnerships reported on a one month lag	10.00%
Percentage of limited partnerships employing hedge fund strategies focused on fixed income and equity investments	51.00%	61.00%
Limited partnerships invested in private debt and equity	40.00%	33.00%
Percentage of equity related limited partnership hedge fund strategies	55.00%
Percentage of multistrategy approach limited partnership hedge fund strategies	26.00%
Percentage of distressed investments limited partnership hedge fund strategies	14.00%
Percentage of fixed income limited partnership hedge fund strategies	5.00%
Carrying value of ten largest limited partnerships	$ 775,000,000	$ 893,000,000
Carrying value of limited partnerships as percentage of aggregate partnership equity	2.00%	2.00%
Income as percentage of change in partnership equity for all limited partnerships	2.00%	2.00%	3.00%
Obligation to return cash	$ 0	$ 0
Notional value	190,000,000	182,000,000
Derivative liability, fair value, gross liability	(19,000,000)	(7,000,000)
Commitments to purchase or fund privately placed debt securities	1,210,000,000
Commitments to sell various privately placed debt securities	85,000,000
Carrying value of securities deposited under requirements of regulatory authorities	3,000,000,000.0	2,700,000,000
Cash and securities deposited as collateral for letters of credit	1,100,000,000	1,100,000,000
5.750% face amount of $400, due August 15, 2021 \| Senior Notes
Gain (Loss) on Securities [Line Items]
Realized investment gains (losses)	(20,000,000)
Face amount	400,000,000
5.875% face amount of $500, due August 15, 2020 \| Senior Notes
Gain (Loss) on Securities [Line Items]
Realized investment gains (losses)		(21,000,000)
Face amount		500,000,000
Common Stock
Gain (Loss) on Securities [Line Items]
Equity securities, FV-NI, gain (loss)	34,000,000	38,000,000
Non-redeemable preferred stock
Gain (Loss) on Securities [Line Items]
Equity securities, FV-NI, gain (loss)	(3,000,000)	66,000,000
Fixed maturity securities
Gain (Loss) on Securities [Line Items]
Interest receivable	371,000,000
OCI, debt securities, available-for-sale, gain (loss), after adjustment, before tax	1,637,000,000	$ 2,620,000,000	$ (1,811,000,000)
Mortgage loans
Gain (Loss) on Securities [Line Items]
Interest receivable	$ 4,000,000

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