General - Statement of Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	$ 851	$ 717	$ 2,143	$ 1,723
Unrealized net capital gains and losses	682	(133)	1,656	(698)
Unrealized foreign currency translation adjustments	4	(6)	9	(8)
Change in unamortized pension and other postretirement prior service credit	(11)	(16)	(23)	(30)
Other comprehensive income (loss), after-tax	675	(155)	1,642	(736)
Comprehensive income	1,526	562	3,785	987
Previously reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	920	676	2,207	1,651
Unrealized net capital gains and losses	682	(133)	1,656	(698)
Unrealized foreign currency translation adjustments	7	(7)	14	(11)
Change in unamortized pension and other postretirement prior service credit	125	22	135	45
Other comprehensive income (loss), after-tax	814	(118)	1,805	(664)
Comprehensive income	1,734	558	4,012	987
Impact of change | Impact of change
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	(69)	41	(64)	72
Unrealized net capital gains and losses	0	0	0	0
Unrealized foreign currency translation adjustments	(3)	1	(5)	3
Change in unamortized pension and other postretirement prior service credit	(136)	(38)	(158)	(75)
Other comprehensive income (loss), after-tax	(139)	(37)	(163)	(72)
Comprehensive income	$ (208)	$ 4	$ (227)	$ 0