Condensed Consolidated Statements of Changes in Shareholder's Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Deficit)
Beginning Balance at Dec. 31, 2016	$ 3,377	$ 3	$ 2,994	$ 560	$ (180)
Comprehensive income (loss):
Net income (loss)	28	0	0	0	28
Other comprehensive income (loss), after tax	186	0	0	186	0
Comprehensive income (loss)	214
Dividends paid and distributions of capital	(261)	0	(261)	0	0
Employee related benefits	0	0	0	0	0
Ending Balance at Jun. 30, 2017	3,330	3	2,733	746	(152)
Increase (Decrease) in Stockholders' Equity
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2014-09	72	0	0	0	72
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-01	0	0	0	(12)	12
Beginning Balance (Scenario, Previously Reported [Member]) at Dec. 31, 2017	3,581	3	2,730	818	30
Beginning Balance at Dec. 31, 2017	3,581
Balance as adjusted at Dec. 31, 2017	3,653	3	2,730	806	114
Comprehensive income (loss):
Net income (loss)	186	0	0	0	186
Other comprehensive income (loss), after tax	(546)	0	0	(546)	0
Comprehensive income (loss)	(360)
Dividends paid and distributions of capital	(126)	0	0	0	(126)
Employee related benefits	(1)	0	(1)	0	0
Ending Balance at Jun. 30, 2018	$ 3,166	$ 3	$ 2,729	$ 260	$ 174