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 Gain (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)					23,854,441
Conversion of Notes			201,472		$ 2	201,470
Issuance of convertible notes			124,050			124,050
Adjustment of embedded derivative for debt modification			(24,071)			(24,071)
Issuance of restricted stock awards (in shares)					6,524,088
Issuance of restricted stock awards			1		$ 1
ESPP purchase (in shares)					1,937,825
ESPP purchase			8,500			8,500
Exercise of stock options (in shares)					443,929
Exercise of stock options			4,243			4,243
Stock-based compensation			53,425			53,425
Unrealized loss on available-for-sale securities	$ (23)		(23)					(23)
Change in effective portion of interest rate swap agreement	(8,144)		(5)					(5)			(8,139)
Distributions to noncontrolling interests		(35)									(5,696)
Contribution from noncontrolling interest											4,314
Foreign currency translation adjustment	0
Net loss	$ (147,496)	(219)	(130,415)						(130,415)		(16,861)
Ending balance (in shares) at Sep. 30, 2020					153,796,572
Ending balance at Sep. 30, 2020		189	(22,418)		$ 15	3,054,376		(9)	(3,076,800)		64,909
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 Jun. 30, 2020					130,238,289
Beginning balance at Jun. 30, 2020		118	(316,951)		$ 13	2,747,890		(9)	(3,064,846)		66,302
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of notes (in shares)					19,136,313
Conversion of Notes			160,342		$ 1	160,341
Issuance of convertible notes			124,050			124,050
Issuance of restricted stock awards (in shares)					3,203,935
Issuance of restricted stock awards			1		$ 1
ESPP purchase (in shares)					944,979
ESPP purchase			4,323			4,323
Exercise of stock options (in shares)					273,056
Exercise of stock options			3,235			3,235
Stock-based compensation			14,537			14,537
Unrealized loss on available-for-sale securities	$ 0
Change in effective portion of interest rate swap agreement	573										573
Distributions to noncontrolling interests		(18)									(269)
Proceeds from noncontrolling interest											4,314
Foreign currency translation adjustment	0
Net loss	(17,876)	89	(11,954)						(11,954)		(6,011)
Ending balance (in shares) at Sep. 30, 2020					153,796,572
Ending balance at Sep. 30, 2020		189	(22,418)		$ 15	3,054,376		(9)	(3,076,800)		64,909
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)					2,533,027
ESPP purchase (in shares)					1,945,305
ESPP purchase			10,045			10,045
Exercise of stock options (in shares)					2,597,003
Exercise of stock options			62,065		$ 1	62,064
Stock-based compensation			55,038			55,038
Unrealized loss on available-for-sale securities	0
Change in effective portion of interest rate swap agreement	(4,031)										4,031
Distributions to noncontrolling interests		(37)									(5,285)
Foreign currency translation adjustment	(523)		(269)					(269)			(254)
Net loss	(144,864)	(9)	(131,123)						(131,123)		(13,732)
Ending balance (in shares) at Sep. 30, 2021					175,078,061
Ending balance at Sep. 30, 2021		331	(46,911)		$ 18	3,183,101		(278)	(3,229,752)		46,955
Beginning balance (in shares) at Jun. 30, 2021					173,402,160
Beginning balance at Jun. 30, 2021		334	(21,571)		$ 17	3,155,917		(124)	(3,177,381)		51,185
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock awards (in shares)					581,363
Issuance of restricted stock awards			0		$ 0
ESPP purchase (in shares)					967,797
ESPP purchase			5,319			5,319
Exercise of stock options (in shares)					126,741
Exercise of stock options			1,123		$ 1	1,122
Stock-based compensation			20,743			20,743
Unrealized loss on available-for-sale securities	0
Change in effective portion of interest rate swap agreement	(763)										763
Distributions to noncontrolling interests		(20)									(540)
Foreign currency translation adjustment	(299)		(154)					(154)			(145)
Net loss	$ (56,662)	17	(52,371)						(52,371)		(4,308)
Ending balance (in shares) at Sep. 30, 2021					175,078,061
Ending balance at Sep. 30, 2021		$ 331	$ (46,911)		$ 18	$ 3,183,101		$ (278)	$ (3,229,752)		$ 46,955