Quarterly Results (Unaudited) Level 4 (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 577	$ 533	$ 595	$ 527	$ 571	$ 702	$ 622	$ 487	$ 2,232	$ 2,382	$ 2,499
Total benefits, losses and expenses	503	462	450	441	464	610	474	478	$ 1,856	$ 2,026	$ 1,969
Net income	$ (316)	$ 83	$ 112	$ 75	$ 57	$ 79	$ 118	$ 28