CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Common stock	Common stock Class B common stock	Additional paid-in capital	Treasury stock	Retained earnings (deficit)	Retained earnings (deficit) Cumulative Effect, Period of Adoption, Adjustment	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	$ 6	$ 0	$ 0	$ 9,549	$ (5,742)	$ 517	$ 6	$ (220)	$ 1,547
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	87						80			7
Other comprehensive income (loss), net of taxes	2								4	(2)
Payment of dividends to common stockholders	(95)						(95)
Proceeds from exercise of equity instruments and employee stock purchase plans (in shares)			2,609,200
Proceeds from exercise of equity instruments and employee stock purchase plans	156				156
Withholding taxes for stock options	(2)				(2)
Treasury stock activity related to vesting of equity instruments (in shares)						225,626
Treasury stock activity related to vesting of equity instruments	(29)					$ (29)
Other changes in ownership of non-controlling interests	10				(3)					13
Stock-based compensation expense	119				119
Other	2				2
Ending balance (in shares) at Jun. 30, 2019			234,102,186	12,799,999		97,384,212
Ending balance at Jun. 30, 2019	5,907		$ 0	$ 0	9,821	$ (5,771)	508		(216)	1,565
Beginning balance (in shares) at Mar. 31, 2019			233,294,034	12,799,999		97,355,708
Beginning balance at Mar. 31, 2019	5,634		$ 0	$ 0	9,694	$ (5,767)	373		(217)	1,551
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	187						183			4
Other comprehensive income (loss), net of taxes	7								1	6
Payment of dividends to common stockholders	(48)						(48)
Proceeds from exercise of equity instruments and employee stock purchase plans (in shares)			808,152
Proceeds from exercise of equity instruments and employee stock purchase plans	65				65
Withholding taxes for stock options	(2)				(2)
Treasury stock activity related to vesting of equity instruments (in shares)						28,504
Treasury stock activity related to vesting of equity instruments	(4)					$ (4)
Other changes in ownership of non-controlling interests	4									4
Stock-based compensation expense	63				63
Other	1				1
Ending balance (in shares) at Jun. 30, 2019			234,102,186	12,799,999		97,384,212
Ending balance at Jun. 30, 2019	5,907		$ 0	$ 0	9,821	$ (5,771)	508		(216)	1,565
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)	(2,137)						(2,037)			(100)
Other comprehensive income (loss), net of taxes	(56)								(56)
Payment of dividends to common stockholders	(48)						(48)
Proceeds from exercise of equity instruments and employee stock purchase plans (in shares)			2,393,155
Proceeds from exercise of equity instruments and employee stock purchase plans	96				96
Treasury stock activity related to vesting of equity instruments (in shares)						393,099
Treasury stock activity related to vesting of equity instruments	(44)					$ (44)
Other changes in ownership of non-controlling interests	10				10
Stock-based compensation expense	118				118
Other	1				1
Other (in shares)						20,630
Common stock warrants, net of issuance costs	$ 110				110
Common stock repurchases (in shares)	3,400,000					3,364,119
Common stock repurchases	$ (370)					$ (370)
Payment of preferred dividends	(17)				(17)
Adjustment to the fair value of redeemable non-controlling interests	4				4
Ending balance (in shares) at Jun. 30, 2020			259,084,932	12,799,999		130,670,373
Ending balance at Jun. 30, 2020	3,203		$ 0	$ 0	13,300	$ (10,087)	(1,206)		(273)	1,469
Beginning balance (in shares) at Mar. 31, 2020			258,769,812	12,799,999		130,592,112
Beginning balance at Mar. 31, 2020	3,741		$ 0	$ 0	13,124	$ (10,083)	(470)		(301)	1,471
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(740)						(736)			(4)
Other comprehensive income (loss), net of taxes	34								28	6
Proceeds from exercise of equity instruments and employee stock purchase plans (in shares)			315,120
Proceeds from exercise of equity instruments and employee stock purchase plans	10				10
Treasury stock activity related to vesting of equity instruments (in shares)						57,631
Treasury stock activity related to vesting of equity instruments	(4)					$ (4)
Other changes in ownership of non-controlling interests	5				9					(4)
Stock-based compensation expense	59				59
Other	1				1
Other (in shares)						20,630
Common stock warrants, net of issuance costs	110				110
Payment of preferred dividends	(17)				(17)
Adjustment to the fair value of redeemable non-controlling interests	4				4
Ending balance (in shares) at Jun. 30, 2020			259,084,932	12,799,999		130,670,373
Ending balance at Jun. 30, 2020	$ 3,203		$ 0	$ 0	$ 13,300	$ (10,087)	$ (1,206)		$ (273)	$ 1,469