Consolidated Statements of Equity (Unaudited) - USD ($) $ in Thousands		Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Deficit [Member]
Balance at Dec. 31, 2019		$ 1,498,996	$ 842	$ 987,942	$ 78	$ 510,134	[1]
Balance, Shares at Dec. 31, 2019			84,248,000
Net income (loss)		(18,712)				(18,712)	[1]
Unrealized holding loss on investments, net of tax		(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			78,000
Issuance of restricted stock			$ 10	(10)
Issuance of restricted stock, shares			968,000
Forfeitures of restricted stock, shares			(19,000)
Stock-based compensation expense		8,035		8,035
Repurchased common stock		(2,542)	$ (1)	(2,541)
Repurchased common stock, shares			(125,000)
Balance at Mar. 31, 2020		1,487,396	$ 852	995,257	(135)	491,422	[1]
Balance, Shares at Mar. 31, 2020			85,150,000
Balance at Dec. 31, 2019		1,498,996	$ 842	987,942	78	510,134	[1]
Balance, Shares at Dec. 31, 2019			84,248,000
Net income (loss)		(691,148)
Balance at Jun. 30, 2020		826,570	$ 855	1,004,786	1,943	181,014	[1]
Balance, Shares at Jun. 30, 2020			85,536,000
Balance at Mar. 31, 2020		1,487,396	$ 852	995,257	(135)	491,422	[1]
Balance, Shares at Mar. 31, 2020			85,150,000
Net income (loss)		(672,436)				(672,436)	[1]
Unrealized holding loss on investments, net of tax		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			277,000
Issuance of restricted stock			$ 2	(2)
Issuance of restricted stock, shares			200,000
Forfeitures of restricted stock			$ (1)	1
Forfeitures of restricted stock, shares			(57,000)
Stock-based compensation expense		7,489		7,489
Repurchased common stock		(501)	$ (1)	(500)
Repurchased common stock, shares			(34,000)
Balance at Jun. 30, 2020		826,570	$ 855	1,004,786	1,943	181,014	[1]
Balance, Shares at Jun. 30, 2020			85,536,000
Balance at Dec. 31, 2020		747,717	$ 856	1,029,453	3,530	(286,122)	[1]
Balance, Shares at Dec. 31, 2020			85,593,000
Net income (loss)		17,642				17,642	[1]
Net loss attributable to noncontrolling interest	[1]	(8)				(8)
Unrealized holding loss on investments, net of tax		(1,133)			(1,133)
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan		1,042		1,042
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan, shares			52,000
Issuance of restricted stock			$ 7	(7)
Issuance of restricted stock, shares			660,000
Forfeitures of restricted stock, shares			(13,000)
Stock-based compensation expense		3,717		3,717
Repurchased common stock		(1,994)	$ (1)	(1,993)
Repurchased common stock, shares			(82,000)
Balance at Mar. 31, 2021		766,983	$ 862	1,032,212	2,397	(268,488)	[1]
Balance, Shares at Mar. 31, 2021			86,210,000
Balance at Dec. 31, 2020		747,717	$ 856	1,029,453	3,530	(286,122)	[1]
Balance, Shares at Dec. 31, 2020			85,593,000
Net income (loss)		52,653
Net loss attributable to noncontrolling interest		$ (14)
Repurchased common stock, shares		0
Balance at Jun. 30, 2021		$ 809,124	$ 863	1,039,231	2,513	(233,483)	[1]
Balance at Mar. 31, 2021		766,983	$ 862	1,032,212	2,397	(268,488)	[1]
Balance, Shares at Mar. 31, 2021			86,210,000
Net income (loss)		35,011				(35,011)	[1]
Net loss attributable to noncontrolling interest		(6)				(6)	[1]
Unrealized holding loss on investments, net of tax		116			116
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan		1,536	$ 1	1,535
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan, shares			71,000
Issuance of restricted stock			$ 1	(1)
Issuance of restricted stock, shares			69,000
Forfeitures of restricted stock			$ (1)	1
Forfeitures of restricted stock, shares			(5,000)
Stock-based compensation expense		5,735		5,735
Repurchased common stock		(251)	$ 0	(251)
Repurchased common stock, shares			(8,000)
Balance at Jun. 30, 2021		$ 809,124	$ 863	$ 1,039,231	$ 2,513	$ (233,483)	[1]

[1] Presented within retained earnings on the consolidated balance sheet as the balance is immaterial.