Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands		Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained (Deficit) Earnings [Member]
Balance at Dec. 31, 2018		$ 3,087,884	$ 878	$ 992,647	$ 2,094,359
Balance, Shares at Dec. 31, 2018			87,820
Net loss		(242,872)			(242,872)
Unrealized holding gain (loss) on investments, net of tax		(194)			(194)
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan		3,542	$ 1	3,541
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan, shares			140
Issuance of restricted stock and conversion of restricted stock units to common stock			$ 10	(10)
Issuance of restricted stock and conversion of restricted stock units to common stock, shares			978
Forfeitures of restricted stock, shares			(6)
Stock swaps		(666)		(666)
Stock swaps, shares			(20)
Stock-based compensation expense		11,100		11,100
Repurchased common stock		(78,982)	$ (25)	(28,740)	(50,217)
Repurchased common stock, shares			(2,525)
Balance at Mar. 31, 2019		2,779,812	$ 864	977,872	1,801,076
Balance, Shares at Mar. 31, 2019			86,387
Balance at Dec. 31, 2018		3,087,884	$ 878	992,647	2,094,359
Balance, Shares at Dec. 31, 2018			87,820
Net loss		(1,507,033)
Balance at Sep. 30, 2019		1,479,360	$ 842	977,709	500,809
Balance, Shares at Sep. 30, 2019			84,185
Balance at Mar. 31, 2019		2,779,812	$ 864	977,872	1,801,076
Balance, Shares at Mar. 31, 2019			86,387
Net loss		(8,245)			(8,245)
Unrealized holding gain (loss) on investments, net of tax		232			232
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan		3,675	$ 2	3,673
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan, shares			155
Issuance of restricted stock and conversion of restricted stock units to common stock			$ 1	(1)
Issuance of restricted stock and conversion of restricted stock units to common stock, shares			123
Forfeitures of restricted stock			$ (1)	1
Forfeitures of restricted stock, shares			(61)
Stock-based compensation expense		15,080		15,080
Repurchased common stock		(65,527)	$ (25)	(29,196)	(36,306)
Repurchased common stock, shares			(2,508)
Balance at Jun. 30, 2019		2,725,027	$ 841	967,429	1,756,757
Balance, Shares at Jun. 30, 2019			84,096
Net loss		(1,255,916)			(1,255,916)
Unrealized holding gain (loss) on investments, net of tax		(32)			(32)
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan		2,606	$ 1	2,605
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan, shares			124
Issuance of restricted stock and conversion of restricted stock units to common stock, shares			12
Forfeitures of restricted stock, shares			(27)
Stock-based compensation expense		8,090		8,090
Repurchased common stock		(415)		(415)
Repurchased common stock, shares			(20)
Balance at Sep. 30, 2019		1,479,360	$ 842	977,709	500,809
Balance, Shares at Sep. 30, 2019			84,185
Balance at Dec. 31, 2019		1,498,996	$ 842	987,942	510,212
Balance, Shares at Dec. 31, 2019			84,248
Net loss		(18,712)			(18,712)
Unrealized holding gain (loss) on investments, net of tax	[1]	(213)			(213)
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan		1,832	$ 1	1,831
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan, shares			78
Issuance of restricted stock and conversion of restricted stock units to common stock			$ 10	(10)
Issuance of restricted stock and conversion of restricted stock units to common stock, shares			968
Forfeitures of restricted stock, shares			(19)
Stock-based compensation expense		8,035		8,035
Repurchased common stock		(2,542)	$ (1)	(2,541)
Repurchased common stock, shares			(125)
Balance at Mar. 31, 2020		1,487,396	$ 852	995,257	491,287
Balance, Shares at Mar. 31, 2020			85,150
Balance at Dec. 31, 2019		1,498,996	$ 842	987,942	510,212
Balance, Shares at Dec. 31, 2019			84,248
Net loss		(732,192)
Balance at Sep. 30, 2020		805,006	$ 855	1,023,974	(219,823)
Balance, Shares at Sep. 30, 2020			85,504
Balance at Mar. 31, 2020		1,487,396	$ 852	995,257	491,287
Balance, Shares at Mar. 31, 2020			85,150
Net loss		(672,436)			(672,436)
Unrealized holding gain (loss) on investments, net of tax	[1]	2,078			2,078
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan		2,544	$ 3	2,541
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan, shares			277
Issuance of restricted stock and conversion of restricted stock units to common stock			$ 2	(2)
Issuance of restricted stock and conversion of restricted stock units to common stock, shares			200
Forfeitures of restricted stock			$ (1)	1
Forfeitures of restricted stock, shares			(57)
Stock-based compensation expense		7,489		7,489
Repurchased common stock		(501)	$ (1)	(500)
Repurchased common stock, shares			(34)
Balance at Jun. 30, 2020		826,570	$ 855	1,004,786	(179,071)
Balance, Shares at Jun. 30, 2020			85,536
Net loss		(41,044)			(41,044)
Contribution from noncontrolling Interests	[1]	245			245
Unrealized holding gain (loss) on investments, net of tax	[1]	47			47
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan		1,324	$ 1	1,323
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan, shares			89
Issuance of restricted stock and conversion of restricted stock units to common stock			$ 3	(3)
Issuance of restricted stock and conversion of restricted stock units to common stock, shares			282
Forfeitures of restricted stock			$ (1)	1
Forfeitures of restricted stock, shares			(92)
Stock-based compensation expense		23,316		23,316
Repurchased common stock		(5,452)	$ (3)	(5,449)
Repurchased common stock, shares			(311)
Balance at Sep. 30, 2020		$ 805,006	$ 855	$ 1,023,974	$ (219,823)
Balance, Shares at Sep. 30, 2020			85,504

[1] Presented within retained (deficit) earnings as the balance is immaterial.