Consolidated Statements of Convertible Redeemable Preferred Stock and Stockholders' Deficit - USD ($) $ in Thousands		Total	Common Stock		Additional Paid-In Capital	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit	Redeemable Noncontrolling Interest	Noncontrolling Interest	Convertible Redeemable Preferred Stock	Class A common stock	Class A common stock Common Stock	Class A common stock Additional Paid-In Capital	Class B common stock	Class B common stock Common Stock	Class B common stock Additional Paid-In Capital
Beginning balance (in shares) at Dec. 31, 2016			10,132,220
Beginning balance at Dec. 31, 2016		$ (1,724,954)	$ 1		$ 108,647	$ (542)	$ (2,068,048)	$ 59,320	$ 175,668
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Contributions from noncontrolling interests		13,651							13,651
Issuance of common stock warrant		9,410			9,410
Issuance of common stock (in shares)			64,000
Conversion of redeemable convertible preferred stock into additional paid-in capital		0
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital		0
Conversion of derivative liability into additional paid-in capital		0
Issuance of common stock		1,981			1,981
Issuance of restricted stock awards (in shares)			19,650
Issuance of restricted stock awards		682			682
Exercise of stock options (in shares)			111,601
Exercise of stock options		336			336
Stock-based compensation expense		21,540			21,540
Unrealized loss on available-for-sale securities		12				12
Change in effective portion of interest rate swap agreement		(243)				142		(1)	(384)
Distributions to noncontrolling interests		(13,726)						(4,816)	(8,910)
Net income (loss)		(209,344)					(194,838)	2,486	(16,992)
Ending balance (in shares) at Sep. 30, 2017			10,327,471
Ending balance at Sep. 30, 2017		(1,900,655)	$ 1		142,596	(388)	(2,262,886)	56,989	163,033
Beginning balance (in shares) at Dec. 31, 2016										71,740,162
Beginning balance at Dec. 31, 2016										$ 1,465,841
Ending balance (in shares) at Sep. 30, 2017										71,740,162
Ending balance at Sep. 30, 2017										$ 1,465,841
Beginning balance (in shares) at Jun. 30, 2017			10,282,645
Beginning balance at Jun. 30, 2017		(1,839,388)	$ 1		124,859	(466)	(2,191,055)	55,814	171,459
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock warrant		9,410			9,410
Issuance of common stock (in shares)			5,333
Issuance of common stock		165			165
Issuance of restricted stock awards (in shares)			15,964
Issuance of restricted stock awards		568			568
Exercise of stock options (in shares)			23,529
Exercise of stock options		109			109
Stock-based compensation expense		7,485			7,485
Unrealized loss on available-for-sale securities		12				12
Change in effective portion of interest rate swap agreement		60				66		(2)	(4)
Distributions to noncontrolling interests		(2,718)						(288)	(2,430)
Net income (loss)		(76,358)					(71,831)	1,465	(5,992)
Ending balance (in shares) at Sep. 30, 2017			10,327,471
Ending balance at Sep. 30, 2017		$ (1,900,655)	$ 1		142,596	(388)	(2,262,886)	56,989	163,033
Beginning balance (in shares) at Jun. 30, 2017										71,740,162
Beginning balance at Jun. 30, 2017										$ 1,465,841
Ending balance (in shares) at Sep. 30, 2017										71,740,162
Ending balance at Sep. 30, 2017										$ 1,465,841
Beginning balance (in shares) at Dec. 31, 2017		10,353,269	10,353,269								0			0
Beginning balance at Dec. 31, 2017		$ (1,966,478)	$ 1		150,804	(162)	(2,330,647)	58,154	155,372
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)			166,667									20,700,000			5,734,440
Issuance of Class A and B common stock upon exercise of warrants (in shares)		312,575	312,575
Issuance of Class A and B common stock upon exercise of warrants	[1]		$ 0
Conversion of redeemable convertible preferred stock Series A-G			71,740,162
Conversion of redeemable convertible preferred stock into additional paid-in capital		$ 1,465,841	$ 7		1,465,834
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital		882			882
Conversion of derivative liability into additional paid-in capital		177,208			177,208
Issuance of common stock		2,500	$ 0	[1]	2,500						$ 282,280	$ 2	$ 282,278	$ 221,580	$ 1	$ 221,579
Issuance of restricted stock awards (in shares)			17,793
Issuance of restricted stock awards		478	$ 0	[1]	478
Exercise of stock options (in shares)			375,391
Exercise of stock options		1,456	$ 0	[1]	1,456
Stock-based compensation expense		84,342			84,342
Unrealized loss on available-for-sale securities		25				25
Change in effective portion of interest rate swap agreement		5,156				409		2	4,745
Distributions to noncontrolling interests		(13,904)						(6,501)	(7,403)
Net income (loss)		$ (155,046)					(141,972)	4,791	(17,865)
Ending balance (in shares) at Sep. 30, 2018		0	109,400,297								20,865,308			88,534,989
Ending balance at Sep. 30, 2018		$ 106,320	$ 11		2,387,361	272	(2,472,619)	56,446	134,849
Beginning balance (in shares) at Dec. 31, 2017		71,740,162								71,740,162
Beginning balance at Dec. 31, 2017		$ 1,465,841								$ 1,465,841
Increase (Decrease) in Temporary Equity [Roll Forward]
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)
Ending balance (in shares) at Sep. 30, 2018		0								0				71,740,162
Ending balance at Sep. 30, 2018		$ 0								$ 0
Beginning balance (in shares) at Jun. 30, 2018			10,570,641
Beginning balance at Jun. 30, 2018		(2,030,647)	$ 1		166,803	216	(2,394,040)	54,940	141,433
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)			166,667												5,734,440
Issuance of Class A common stock upon public offering, net (in shares)												20,700,000
Issuance of Class A common stock upon public offering, net											$ 282,280	$ 2	$ 282,278
Issuance of Class A and B common stock upon exercise of warrants (in shares)			312,575
Issuance of Class A and B common stock upon exercise of warrants	[1]		$ 0
Conversion of redeemable convertible preferred stock Series A-G			71,740,162
Conversion of redeemable convertible preferred stock into additional paid-in capital		1,465,841	$ 7		1,465,834
Reclassification of redeemable convertible preferred stock warrant liability to additional paid-in capital		882			882
Conversion of derivative liability into additional paid-in capital		177,208			177,208
Issuance of common stock		2,500	$ 0	[1]	2,500									$ 221,580	$ 1	$ 221,579
Issuance of restricted stock awards (in shares)			14,178
Issuance of restricted stock awards		238	$ 0	[1]	238
Exercise of stock options (in shares)			161,634
Exercise of stock options		714	$ 0	[1]	714
Stock-based compensation expense		69,325			69,325
Unrealized loss on available-for-sale securities		1				1
Change in effective portion of interest rate swap agreement		1,240				55		0	1,185
Distributions to noncontrolling interests		(2,332)							(2,044)
Net income (loss)		$ (82,510)					(78,579)	1,794	(5,725)
Ending balance (in shares) at Sep. 30, 2018		0	109,400,297								20,865,308			88,534,989
Ending balance at Sep. 30, 2018		$ 106,320	$ 11		$ 2,387,361	$ 272	$ (2,472,619)	$ 56,446	$ 134,849
Beginning balance (in shares) at Jun. 30, 2018										71,740,162
Beginning balance at Jun. 30, 2018										$ 1,465,841
Increase (Decrease) in Temporary Equity [Roll Forward]
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)
Ending balance (in shares) at Sep. 30, 2018		0								0				71,740,162
Ending balance at Sep. 30, 2018		$ 0								$ 0

[1] Amounts are less than $0.5 thousand and round down to zero