Consolidated Statements of Comprehensive Income (Unaudited) (Parentheticals) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Tax effect on benefit obligation	$ 2	$ 2	$ 6	$ 3
Tax effect on net unrealized gains on investments during the period	$ 1	$ 1	$ 1	$ 1