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
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 restricted stock awards (in shares)	[1]			68,098
Issuance of restricted stock awards			120			120
Exercise of stock options (in shares)	[1]			3,615
Exercise of stock options			67			67
Stock-based compensation expense			7,614			7,614
Excess fair value of consideration paid over the noncontrolling interest reduction		$ (9)	(9)				(9)
Change in effective and ineffective portion of interest rate swap agreement		2,867	288				288		3	2,576
Distributions to noncontrolling interests									(1,472)	(2,066)
Net income (loss)		(22,348)							1,491	(6,123)
Net loss attributable to Class A and Class B common stockholders		(17,716)	(17,716)					(17,716)
Ending balance (in shares) at Mar. 31, 2018	[1]			10,424,982
Ending balance at Mar. 31, 2018			(2,189,641)	$ 1	[1]	158,604	117	(2,348,363)
Ending balance at Mar. 31, 2018									58,176	149,759
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 Mar. 31, 2018											71,740,162
Ending balance at Mar. 31, 2018											$ 1,465,841
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 restricted stock awards (in shares)				2,960,462
ESPP purchase (in shares)				696,036
ESPP purchase			6,916			6,916
Exercise of stock options (in shares)				136,382
Exercise of stock options			577			577
Stock-based compensation expense			63,166			63,166
Excess fair value of consideration paid over the noncontrolling interest reduction		17	17				17
Change in effective and ineffective portion of interest rate swap agreement		(2,191)	(143)				(143)			(2,048)
Distributions to noncontrolling interests									(282)	(2,613)
Net income (loss)		(88,273)							1,823	(5,655)
Net loss attributable to Class A and Class B common stockholders		(84,441)	(84,441)					(84,441)
Ending balance (in shares) at Mar. 31, 2019				113,214,063
Ending balance at Mar. 31, 2019		$ (105,439)	$ (105,439)	$ 11		$ 2,551,256	$ 5	$ (2,656,711)
Ending balance at Mar. 31, 2019									$ 58,802	$ 114,664
Beginning balance (in shares) at Dec. 31, 2018											0
Beginning balance at Dec. 31, 2018											$ 0
Ending balance (in shares) at Mar. 31, 2019											0
Ending balance at Mar. 31, 2019											$ 0

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