Income Taxes (Details) - Effective Tax Rate - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S. income before income taxes									$ 3,211	$ 3,039	$ 2,798
Foreign income (loss) before income taxes									(73)	(78)	(68)
Income before income taxes	$ 1,074	$ 432	$ 665	$ 967	$ 746	$ 806	$ 631	$ 778	$ 3,138	$ 2,961	$ 2,730
Statutory tax rate (percent)									21.00%	21.00%	35.00%
Expected federal income tax expense									$ 659	$ 622	$ 956
Tax effect of nontaxable investment income									(149)	(150)	(297)
Tax effect of TCJA at enactment											129
Tax effect of other, net									6	(34)	(114)
Total income tax expense included in the consolidated statement of income	201	$ 36	$ 108	$ 171	125	$ 97	$ 107	$ 109	$ 516	$ 438	$ 674
Effective tax rate (percent)									16.00%	15.00%	25.00%
Income taxes paid									$ 428	$ 408	$ 514
Current income tax payable	126								126
Current income tax receivable					$ 12					$ 12
Net charge included in total income tax expense related to TCJA at the date of enactment											$ 129
Estimated additional annual tax payments relating to the discounted reserves transitional adjustment associated with TCJA	$ 19								$ 19