CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	Common stock	Common stock Class B common stock	Additional paid-in capital	Treasury stock	Retained earnings (deficit)	Accumulated other comprehensive income (loss)	Non-redeemable non-controlling interest
Beginning balance (in shares) at Dec. 31, 2019		256,691,777	12,799,999		126,892,525
Beginning balance at Dec. 31, 2019	$ 5,536	$ 0	$ 0	$ 12,978	$ (9,673)	$ 879	$ (217)	$ 1,569
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(1,397)					(1,301)		(96)
Other comprehensive income (loss), net of taxes	(90)						(84)	(6)
Payment of dividends to common stockholders	(48)					(48)
Proceeds from exercise of equity instruments and employee stock purchase plans (in shares)		2,078,035
Proceeds from exercise of equity instruments and employee stock purchase plans	86	$ 0		86
Treasury stock activity related to vesting of equity instruments (in shares)					335,468
Treasury stock activity related to vesting of equity instruments	$ (40)				$ (40)
Common stock repurchases (in shares)	3,400,000				3,364,119
Common stock repurchases	$ (370)				$ (370)
Other changes in ownership of non-controlling interests	5			1				4
Stock-based compensation expense	59			59
Ending balance (in shares) at Mar. 31, 2020		258,769,812	12,799,999		130,592,112
Ending balance at Mar. 31, 2020	3,741	$ 0	$ 0	13,124	$ (10,083)	(470)	(301)	1,471
Beginning balance (in shares) at Dec. 31, 2020		261,563,912	12,799,999		130,766,537
Beginning balance at Dec. 31, 2020	3,004	$ 0	$ 0	13,566	$ (10,097)	(1,781)	(178)	1,494
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(581)					(578)		(3)
Other comprehensive income (loss), net of taxes	(37)						(21)	(16)
Proceeds from exercise of equity instruments and employee stock purchase plans (in shares)		3,643,100
Proceeds from exercise of equity instruments and employee stock purchase plans	269	$ 0		269
Withholding taxes for stock options	(7)			(7)
Treasury stock activity related to vesting of equity instruments (in shares)					374,806
Treasury stock activity related to vesting of equity instruments	$ (55)				$ (55)
Common stock repurchases (in shares)	0
Other changes in ownership of non-controlling interests	$ 4			0				4
Stock-based compensation expense	91			91
Ending balance (in shares) at Mar. 31, 2021		265,207,012	12,799,999		131,141,343
Ending balance at Mar. 31, 2021	$ 2,688	$ 0	$ 0	$ 13,919	$ (10,152)	$ (2,359)	$ (199)	$ 1,479