Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Unrealized gains on investments available-for-sale, net of tax	$ 317	$ 186	$ (220)
Amortization of pension actuarial loss and prior service cost, net of tax	7	6	(2)
Change in life deferred acquisition costs, life policy reserves and other, net of tax	$ 1	$ (4)	$ 4