Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ (401)	$ 450	$ 311	$ 254	$ 101	$ 314	$ 431	$ 430	$ 614	$ 1,276	$ 1,147
Other comprehensive (loss) income:
Change in gross unrealized investment gains/losses									(101)	(114)	122
Effect of income taxes									38	42	(44)
Total change in unrealized investment gains/losses, net of tax									(63)	(72)	78
Reclassification adjustment for net realized gains included in investment income									(96)	(146)	(20)
Effect of income taxes									35	53	7
Total reclassification adjustment, net of tax									(61)	(93)	(13)
Other comprehensive (loss) income, net of tax									(124)	(165)	65
Comprehensive income									$ 490	$ 1,111	$ 1,212