CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (UNAUDITED) (Parenthetical) - USD ($) $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2019
Income tax expense	$ 172	$ 114		$ 497	$ 369
ACCUMULATED DEFICIT | Cumulative Effect, Period of Adoption, Adjustment
Income tax expense			$ 2			$ 2