Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 86	$ (153)	$ (153)	$ 136
Other comprehensive income (loss):
Fair value change - derivatives, net of tax (expense) benefit ($9, $0, $0, and $0, respectively)		(26)
Foreign currency translation adjustment	3	9	3	(11)
Comprehensive income (loss)	$ 89	$ (170)	$ (150)	$ 125