Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 272	$ 209	$ 532	$ 275
Other Comprehensive Income, Net of Tax
Net unrealized gains on investments with other-than-temporary impairments	0	(1)	(4)	4
Net unrealized gains on other investments	77	310	144	544
Net unrealized gains on investments	77	309	140	548
Foreign currency translation adjustment	42	(48)	53	(34)
Pension and postretirement benefits	5	5	12	11
Other comprehensive income, net of tax	124	266	205	525
Total comprehensive income	$ 396	$ 475	$ 737	$ 800