Quarterly Results (Unaudited) Level 4 (Details) - USD ($) $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended							5 Months Ended	7 Months Ended	12 Months Ended
	Jun. 30, 2018	May 31, 2018	Dec. 31, 2018	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	May 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 156	$ 245	$ 749	$ 317	$ 591	$ 577	$ 533	$ 595	$ 527	$ 836	$ 1,222	$ 2,232	$ 2,382
Total benefits, losses and expenses	85	288	406	263	447	503	462	450	441	$ 735	$ 754	$ 1,856	$ 2,026
Net income	$ 57	$ (31)	$ 285	$ 67	$ 125	$ (316)	$ 83	$ 112	$ 75