Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI, net of tax
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change				$ 0	$ 0
Adjusted balance, beginning of period				2,158	722
Beginning Balance at Dec. 31, 2016			$ 4,935	2,158	722
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Return of capital to parent			(298)
Net income (loss)	$ 75			75
Other Comprehensive Income (Loss), Net of Tax					37
Ending Balance at Mar. 31, 2017	7,635	$ 6	4,637	2,233	759
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change				(182)	182
Adjusted balance, beginning of period				1,930	1,205
Beginning Balance at Dec. 31, 2017	6,680		3,539	2,112	1,023
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Return of capital to parent			2
Net income (loss)	125			125
Other Comprehensive Income (Loss), Net of Tax					(321)
Ending Balance at Mar. 31, 2018	$ 6,486	$ 6	$ 3,541	$ 2,055	$ 884