Summary of Significant Accounting Policies - Adoption of Topic 606 and ASC 842, Statement of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cost of customer agreements and incentives										$ 186,435	$ 154,244
Sales and marketing									$ 207,232	146,426	168,737
General and administrative									116,659	107,400	92,416
Interest expense, net									131,771	92,255	73,340
Income tax expense									9,322	12,353	56,263
Net loss	$ (49,515)	$ (47,524)	$ (71,727)	$ (91,420)	$ (56,035)	$ (82,815)	$ (73,610)	$ (75,155)	(260,186)	(287,615)	(320,839)
Net loss attributable to noncontrolling interests and redeemable noncontrolling interests									(286,843)	(413,104)	(395,968)
Net income attributable to common stockholders	$ (5,888)	$ (2,896)	$ 7,409	$ 28,032	$ 69,254	$ 28,007	$ 18,346	$ 9,882	$ 26,657	$ 125,489	$ 75,129
Basic (in dollars per share)	$ (0.05)	$ (0.03)	$ 0.07	$ 0.26	$ 0.65	$ 0.26	$ 0.17	$ 0.09	$ 0.24	$ 1.19	$ 0.73
Diluted (in dollars per share)	$ (0.05)	$ (0.02)	$ 0.06	$ 0.25	$ 0.63	$ 0.26	$ 0.17	$ 0.09	$ 0.23	$ 1.16	$ 0.72
Customer agreements and incentives
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Customer agreements and incentives									$ 404,466	$ 234,276	$ 191,626
Previously Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cost of customer agreements and incentives										193,954	159,858
Sales and marketing										137,115	162,781
General and administrative										107,420	92,377
Interest expense, net										70,518	53,244
Income tax expense										32,138	35,993
Net loss										(286,734)	(303,301)
Net loss attributable to noncontrolling interests and redeemable noncontrolling interests										(411,259)	(394,988)
Net income attributable to common stockholders										$ 124,525	$ 91,687
Basic (in dollars per share)										$ 1.18	$ 0.90
Diluted (in dollars per share)										$ 1.15	$ 0.87
Previously Reported | Customer agreements and incentives
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Customer agreements and incentives										$ 231,433	$ 168,417
Adoption Impact | Accounting Standards Update 2014-09 and ASC 842
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cost of customer agreements and incentives										(7,519)	(5,614)
Sales and marketing										9,311	5,956
General and administrative										(20)	39
Interest expense, net										21,737	20,096
Income tax expense										(19,785)	20,270
Net loss										(881)	(17,538)
Net loss attributable to noncontrolling interests and redeemable noncontrolling interests										(1,845)	(980)
Net income attributable to common stockholders										$ 964	$ (16,558)
Basic (in dollars per share)										$ 0.01	$ (0.17)
Diluted (in dollars per share)										$ 0.01	$ (0.15)
Adoption Impact | Accounting Standards Update 2014-09 and ASC 842 | Customer agreements and incentives
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Customer agreements and incentives										$ 2,843	$ 23,209