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, 2018		231,492,986	12,799,999		97,158,586
Beginning balance at Dec. 31, 2018	$ 5,651	$ 0	$ 0	$ 9,549	$ (5,742)	$ 517	$ (220)	$ 1,547
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(100)					(103)		3
Other comprehensive income (loss), net of taxes	(5)						3	(8)
Payment of dividends to stockholders	(47)					(47)
Proceeds from exercise of equity instruments and employee stock purchase plans (in shares)		1,801,048
Proceeds from exercise of equity instruments and employee stock purchase plans	91			91
Treasury stock activity related to vesting of equity instruments (in shares)					197,122
Treasury stock activity related to vesting of equity instruments	(25)				$ (25)
Other changes in ownership of non-controlling interests	6			(3)				9
Impact of adoption of new accounting guidance	6					6
Stock-based compensation expense	56			56
Other	(1)			1
Ending balance (in shares) at Mar. 31, 2019		233,294,034	12,799,999		97,355,708
Ending balance at Mar. 31, 2019	5,634	$ 0	$ 0	9,694	$ (5,767)	373	(217)	1,551
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 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			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)
Other changes in ownership of non-controlling interests	5			1				4
Stock-based compensation expense	$ 59			59
Stock repurchases (in shares)	3,400,000				3,364,119
Common stock repurchases	$ (370)				$ (370)
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