CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 197	$ (97)	$ 506	$ (250)
Other comprehensive income (loss):
Unrealized investment gain (loss)	1	1	(5)	2
Less: effect of income taxes	0	1	(1)	1
Other comprehensive income (loss), net of tax	1	0	(4)	1
Comprehensive income (loss)	$ 198	$ (97)	$ 502	$ (249)

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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