Income Taxes (Details) - Effective Tax Rate - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Nov. 30, 2018	Oct. 31, 2018
Income Tax Disclosure [Abstract]
U.S. income before income taxes									$ 3,039	$ 2,798	$ 3,946
Foreign income (loss) before income taxes									(78)	(68)	107
Income before income taxes	$ 746	$ 806	$ 631	$ 778	$ 860	$ 320	$ 790	$ 760	$ 2,961	$ 2,730	$ 4,053
Statutory tax rate (percent)									21.00%	35.00%	35.00%
Expected federal income tax expense									$ 622	$ 956	$ 1,419
Tax effect of nontaxable investment income									(150)	(297)	(323)
Tax effect of TCJA at enactment										129
Tax effect of other, net									(34)	(114)	(57)
Total income tax expense included in the consolidated statement of income	125	$ 97	$ 107	$ 109	309	$ 27	$ 195	$ 143	$ 438	$ 674	$ 1,039
Effective tax rate (percent)									15.00%	25.00%	26.00%
Income taxes paid									$ 408	$ 514	$ 892
Current income tax receivable	12				$ 65				12	$ 65
Estimated additional annual tax payments relating to the discounted reserves transitional adjustment associated with TCJA	$ 23								$ 23			$ 23	$ 70