Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 3,189	$ 1,877	$ 2,171
Changes in:
Unrealized net capital gains and losses	319	433	(1,306)
Unrealized foreign currency translation adjustments	47	10	(58)
Unrecognized pension and other postretirement benefit cost	307	(104)	48
Other comprehensive income (loss), after-tax	673	339	(1,316)
Comprehensive income	$ 3,862	$ 2,216	$ 855