General - Statement of Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	$ 1,292	$ 1,006
Unrealized net capital gains and losses	974	(565)
Unrealized foreign currency translation adjustments	5	(2)
Change in unamortized pension and other postretirement prior service credit	(12)	(14)
Other comprehensive income (loss), after-tax	967	(581)
Comprehensive income	2,259	425
Previously reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	1,287	975
Unrealized net capital gains and losses	974	(565)
Unrealized foreign currency translation adjustments	7	(4)
Change in unamortized pension and other postretirement prior service credit	10	23
Other comprehensive income (loss), after-tax	991	(546)
Comprehensive income	2,278	429
Impact of change | Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	5	31
Unrealized net capital gains and losses	0	0
Unrealized foreign currency translation adjustments	(2)	2
Change in unamortized pension and other postretirement prior service credit	22	(37)
Other comprehensive income (loss), after-tax	(24)	(35)
Comprehensive income	$ (19)	$ (4)