Condensed Consolidated Statements of Convertible Redeemable Preferred Stock, Redeemable Noncontrolling Interest, Stockholders' Deficit and Noncontrolling Interest (unaudited) - USD ($) $ in Thousands		Total	Stockholders' Deficit	Common Stock		Additional Paid-In Capital	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit	Redeemable Noncontrolling Interest	Noncontrolling Interest	Convertible Redeemable Preferred Stock	Class B common stock Stockholders' Deficit	Class B common stock Common Stock		Class B common stock Additional Paid-In Capital	Class A common stock Stockholders' Deficit	Class A common stock Common Stock		Class A common stock Additional Paid-In Capital
Beginning balance (in shares) at Dec. 31, 2017	[1]			10,353,269
Beginning balance at Dec. 31, 2017			$ (2,180,005)	$ 1	[1]	$ 150,803	$ (162)	$ (2,330,647)
Beginning balance at Dec. 31, 2017									$ 58,154	$ 155,372
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of class A common stock upon public offering, net of underwriting discounts and commissions, and net of offering costs (in shares)	[1]																20,700,000
Issuance of class A common stock upon public offering, net of underwriting discounts and commissions, and net of offering costs																$ 282,280	$ 2	[1]	$ 282,278
Issuance of common stock (in shares)	[1]			166,667									5,734,440
Issuance of common stock			2,500			2,500						$ 221,580	$ 1	[1]	$ 221,579
Issuance of class A and B common stock upon exercise of common stock warrants (in shares)	[1]			312,575
Conversion of redeemable convertible preferred stock Series A through G (to common stock upon public offering) (in shares)	[1]			71,740,162
Conversion of redeemable convertible preferred stock Series A through G (to common stock upon public offering)		$ 1,465,841	1,465,841	$ 7	[1]	1,465,834
Temporary Equity,Conversion of redeemable convertible preferred stock Series A-G (in shares)											(71,740,162)
Temporary Equity, Conversion of redeemable convertible preferred stock Series A-G											$ (1,465,841)
Reclassification of redeemable convertible preferred stock warrant liability to additional paid in capital		882	882			882
Reclassification of derivative liability into additional paid-in capital		177,208	177,208			177,208
Issuance of restricted stock awards (in shares)	[1]			17,793
Issuance of restricted stock awards			305			305
Revaluation of common stock warrants			(66)			(66)
Exercise of stock options (in shares)	[1]			375,391
Exercise of stock options			1,456			1,456
Stock-based compensation expense			84,581			84,581
Unrealized gain/(loss) on available for sale securities		25	92				92
Change in effective portion of interest rate swap agreement		5,156	342				342		2	4,745
Distributions to noncontrolling interests									(6,501)	(7,403)
Net income (loss)		(155,046)	(141,972)					(141,972)	4,791	(17,865)
Ending balance (in shares) at Sep. 30, 2018	[1],[2]			109,400,297
Ending balance at Sep. 30, 2018			(84,976)	$ 11	[1],[2]	2,387,360	272	(2,472,619)
Ending balance at Sep. 30, 2018									56,446	134,849
Beginning balance (in shares) at Dec. 31, 2017											71,740,162
Beginning balance at Dec. 31, 2017											$ 1,465,841
Ending balance (in shares) at Sep. 30, 2018											0
Ending balance at Sep. 30, 2018											$ 0
Beginning balance (in shares) at Jun. 30, 2018	[2]			10,570,641
Beginning balance at Jun. 30, 2018			(2,227,019)	$ 1	[2]	166,803	217	(2,394,040)
Beginning balance at Jun. 30, 2018									54,940	141,433
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of class A common stock upon public offering, net of underwriting discounts and commissions, and net of offering costs (in shares)	[2]																20,700,000
Issuance of class A common stock upon public offering, net of underwriting discounts and commissions, and net of offering costs																$ 282,280	$ 2	[2]	$ 282,278
Issuance of common stock (in shares)	[2]			166,667									5,734,440
Issuance of common stock			2,500			2,500						$ 221,580	$ 1	[2]	$ 221,579
Issuance of class A and B common stock upon exercise of common stock warrants (in shares)	[2]			312,575
Conversion of redeemable convertible preferred stock Series A through G (to common stock upon public offering) (in shares)	[2]			71,740,162
Conversion of redeemable convertible preferred stock Series A through G (to common stock upon public offering)			1,465,841	$ 7	[2]	1,465,834
Temporary Equity,Conversion of redeemable convertible preferred stock Series A-G (in shares)											(71,740,162)
Temporary Equity, Conversion of redeemable convertible preferred stock Series A-G											$ (1,465,841)
Reclassification of redeemable convertible preferred stock warrant liability to additional paid in capital			882			882
Reclassification of derivative liability into additional paid-in capital			177,208			177,208
Issuance of restricted stock awards (in shares)	[2]			14,178
Issuance of restricted stock awards			238			238
Exercise of stock options (in shares)	[2]			161,634
Exercise of stock options			713			713
Stock-based compensation expense			69,325			69,325
Unrealized gain/(loss) on available for sale securities		1	1				1
Change in effective portion of interest rate swap agreement		1,236	54				54			1,182
Distributions to noncontrolling interests									(288)	(2,041)
Net income (loss)		(82,510)	(78,579)					(78,579)	1,794	(5,725)
Ending balance (in shares) at Sep. 30, 2018	[1],[2]			109,400,297
Ending balance at Sep. 30, 2018			(84,976)	$ 11	[1],[2]	2,387,360	272	(2,472,619)
Ending balance at Sep. 30, 2018									56,446	134,849
Beginning balance (in shares) at Jun. 30, 2018											71,740,162
Beginning balance at Jun. 30, 2018											$ 1,465,841
Ending balance (in shares) at Sep. 30, 2018											0
Ending balance at Sep. 30, 2018											$ 0
Beginning balance (in shares) at Dec. 31, 2018				109,421,183
Beginning balance at Dec. 31, 2018		$ (91,661)	(91,661)	$ 11		2,480,597	131	(2,572,400)
Beginning balance at Dec. 31, 2018									57,261	125,110
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of class A and B common stock upon exercise of common stock warrants (in shares)		312,575
Conversion of redeemable convertible preferred stock Series A through G (to common stock upon public offering)		$ 0
Reclassification of redeemable convertible preferred stock warrant liability to additional paid in capital		0
Reclassification of derivative liability into additional paid-in capital		0
Issuance of restricted stock awards (in shares)				6,341,441
Issuance of restricted stock awards			1	$ 1
ESPP purchase (in shares)				1,718,433
ESPP purchase			11,183			11,183
Exercise of stock options (in shares)				336,572
Exercise of stock options			1,440			1,440
Stock-based compensation expense			153,898			153,898
Unrealized gain/(loss) on available for sale securities		14	14				14
Change in effective and ineffective portion of interest rate swap agreement			(292)				(292)			(7,845)
Change in effective portion of interest rate swap agreement		(8,137)
Distributions to noncontrolling interests									(3,825)	(5,250)
Mandatory redemption of noncontrolling interests									(55,684)
Net income (loss)		(195,434)	(181,560)					(181,560)	2,805	(16,679)
Ending balance (in shares) at Sep. 30, 2019				117,817,629
Ending balance at Sep. 30, 2019		(106,847)	(106,847)	$ 12		2,647,118	(147)	(2,753,830)
Ending balance at Sep. 30, 2019									557	95,206
Beginning balance (in shares) at Jun. 30, 2019				113,949,343
Beginning balance at Jun. 30, 2019			(115,785)	$ 11		2,603,279	(148)	(2,718,927)
Beginning balance at Jun. 30, 2019									505	104,072
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock awards (in shares)				2,837,343
Issuance of restricted stock awards			1	$ 1
ESPP purchase (in shares)				1,022,397
ESPP purchase			4,267			4,267
Exercise of stock options (in shares)				8,546
Exercise of stock options			35			35
Stock-based compensation expense			39,537			39,537
Unrealized gain/(loss) on available for sale securities		(12)	(12)				(12)
Change in effective and ineffective portion of interest rate swap agreement			13				13			(2,457)
Change in effective portion of interest rate swap agreement		(2,444)
Distributions to noncontrolling interests									(288)	(1,042)
Net income (loss)		(39,930)	(34,903)					(34,903)	340	(5,367)
Ending balance (in shares) at Sep. 30, 2019				117,817,629
Ending balance at Sep. 30, 2019		$ (106,847)	$ (106,847)	$ 12		$ 2,647,118	$ (147)	$ (2,753,830)
Ending balance at Sep. 30, 2019									$ 557	$ 95,206

[1] Common Stock issued and converted to Class A Common and Class B Common effective July 2018.

[2] Common Stock issued and converted to Class A Common and Class B Common effective July 2018.