Statutory Net Income and Surplus and Dividend Restrictions (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Insurance [Abstract]
Statutory net income	$ (503)	$ 578	$ 593
Statutory surplus	1,365	1,250
Statutory surplus capacity to pay divided without prior approval	0
Statutory dividend paid with approval	$ 250	$ 2,593	$ 430