Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 260	$ 66
Other Comprehensive Income, Net of Tax
Net unrealized gains on investments with other-than-temporary impairments	(4)	5
Net unrealized gains on other investments	67	234
Net unrealized gains on investments	63	239
Foreign currency translation adjustment	11	14
Pension and postretirement benefits	7	6
Other comprehensive income, net of tax	81	259
Total comprehensive income	$ 341	$ 325