Consolidated Statements of Shareholder's Equity (Unaudited) - USD ($) $ in Millions	Total	Common stock	Additional paid- in capital	Accumulated other comprehensive loss	Accumulated deficit
Balance at beginning of period at Dec. 31, 2019	$ 1,019	$ 1	$ 4,333	$ (93)	$ (3,222)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	49			11	38
Balance at end of period at Sep. 30, 2020	1,068	1	4,333	(82)	(3,184)
Balance at beginning of period at Dec. 31, 2020	1,427	1	4,633	(70)	(3,137)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	103			7	96
Balance at end of period at Sep. 30, 2021	$ 1,530	$ 1	$ 4,633	$ (63)	$ (3,041)