Condensed Consolidated Statements of Redeemable Noncontrolling Interest, Stockholders' (Deficit) Equity and Noncontrolling Interest - USD ($) $ in Thousands	Total	Redeemable Noncontrolling  Interest	Total Stockholders' Equity (Deficit)	Total Stockholders' Equity (Deficit) Cumulative effect upon adoption of new accounting standard	Common Stock	Additional Paid-In Capital	Additional Paid-In Capital Cumulative effect upon adoption of new accounting standard	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Accumulated Deficit Cumulative effect upon adoption of new accounting standard	Noncontrolling Interest
Beginning balance (in shares) at Dec. 31, 2019					121,036,289
Beginning balance at Dec. 31, 2019		$ 443	$ (259,594)		$ 12	$ 2,686,759		$ 19	$ (2,946,384)		$ 91,291
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of notes (in shares)					4,718,128
Conversion of Notes			41,130		$ 1	41,129
Adjustment of embedded derivative for debt modification			(24,071)			(24,071)
Issuance of restricted stock awards (in shares)					3,320,153
ESPP purchase (in shares)					992,846
ESPP purchase			4,177			4,177
Exercise of stock options (in shares)					170,873
Exercise of stock options			1,008			1,008
Stock-based compensation			38,888			38,888
Unrealized loss on available-for-sale securities	$ (23)		(23)					(23)
Change in effective portion of interest rate swap agreement	(8,717)		(5)					(5)			(8,712)
Distributions to noncontrolling interests		(17)									(5,427)
Foreign currency translation adjustment	0
Net income (loss)	$ (129,620)	(308)	(118,461)						(118,461)		(10,850)
Ending balance (in shares) at Jun. 30, 2020					130,238,289
Ending balance at Jun. 30, 2020		118	(316,951)		$ 13	2,747,890		(9)	(3,064,845)		66,302
Beginning balance (in shares) at Dec. 31, 2019					121,036,289
Beginning balance at Dec. 31, 2019		443	(259,594)		$ 12	2,686,759		19	(2,946,384)		91,291
Ending balance (in shares) at Dec. 31, 2020					168,002,726
Ending balance at Dec. 31, 2020		377	78,824	$ (121,491)	$ 17	3,182,753	$ (126,799)	(9)	(3,103,937)	$ 5,308	62,195
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	Accounting Standards Update 2020-06
Beginning balance (in shares) at Mar. 31, 2020					125,150,690
Beginning balance at Mar. 31, 2020		67	(333,099)		$ 12	2,689,208		14	(3,022,333)		73,867
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of notes (in shares)					4,718,128
Conversion of Notes			41,130		$ 1	41,129
Issuance of restricted stock awards (in shares)					309,547
Exercise of stock options (in shares)					59,924
Exercise of stock options			341			341
Stock-based compensation			17,212			17,212
Unrealized loss on available-for-sale securities	$ (23)		(23)					(23)
Change in effective portion of interest rate swap agreement	(503)										(503)
Distributions to noncontrolling interests		(16)									(1,530)
Foreign currency translation adjustment	0
Net income (loss)	(47,978)	67	(42,512)						(42,512)		(5,532)
Ending balance (in shares) at Jun. 30, 2020					130,238,289
Ending balance at Jun. 30, 2020		118	(316,951)		$ 13	2,747,890		(9)	(3,064,845)		66,302
Beginning balance (in shares) at Dec. 31, 2020					168,002,726
Beginning balance at Dec. 31, 2020		377	78,824	$ (121,491)	$ 17	3,182,753	$ (126,799)	(9)	(3,103,937)	$ 5,308	62,195
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock awards (in shares)					1,951,664
ESPP purchase (in shares)					977,508
ESPP purchase			4,726			4,726
Exercise of stock options (in shares)					2,470,262
Exercise of stock options			60,942			60,942
Stock-based compensation			34,295			34,295
Unrealized loss on available-for-sale securities	0
Change in effective portion of interest rate swap agreement	(3,268)										3,268
Distributions to noncontrolling interests		(17)									(4,745)
Foreign currency translation adjustment	(224)		(115)					(115)	0		(109)
Net income (loss)	(88,202)	(26)	(78,752)						(78,752)		(9,424)
Ending balance (in shares) at Jun. 30, 2021					173,402,160
Ending balance at Jun. 30, 2021		334	(21,571)		$ 17	3,155,917		(124)	(3,177,381)		51,185
Beginning balance (in shares) at Mar. 31, 2021					172,099,453
Beginning balance at Mar. 31, 2021		356	6,060		$ 17	3,129,687		(126)	(3,123,518)		57,986
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock awards (in shares)					811,162
Exercise of stock options (in shares)					491,545
Exercise of stock options			7,715			7,715
Stock-based compensation			18,515			18,515
Unrealized loss on available-for-sale securities	0
Change in effective portion of interest rate swap agreement	1,385										(1,385)
Distributions to noncontrolling interests											(882)
Foreign currency translation adjustment	4		2					2			2
Net income (loss)	$ (58,421)	(22)	(53,863)						(53,863)		(4,536)
Ending balance (in shares) at Jun. 30, 2021					173,402,160
Ending balance at Jun. 30, 2021		$ 334	$ (21,571)		$ 17	$ 3,155,917		$ (124)	$ (3,177,381)		$ 51,185