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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue: Customer agreements and incentives	$ 91,605	$ 58,111	$ 158,595	$ 107,201
Cost of customer agreements and incentives	57,769	45,289	112,345	87,902
Sales and marketing	49,237	35,056	93,316	68,188
General and administrative	28,130	25,228	61,023	49,836
Interest expense, net	31,872	21,971	60,070	42,529
Income tax expense	4,378	10,781	12,581	16,181
Net loss	(71,727)	(73,610)	(163,147)	(148,765)
Net loss attributable to noncontrolling interests and redeemable noncontrolling interests	(79,136)	(91,956)	(198,588)	(176,993)
Net income available to common stockholders	$ 7,409	$ 18,346	$ 35,441	$ 28,228
Basic (in dollars per share)	$ 0.07	$ 0.17	$ 0.33	$ 0.27
Diluted (in dollars per share)	$ 0.06	$ 0.17	$ 0.31	$ 0.26
Previously Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue: Customer agreements and incentives		$ 65,337		$ 113,435
Cost of customer agreements and incentives		47,114		91,450
Sales and marketing		32,784		64,460
General and administrative		25,230		49,851
Interest expense, net		16,602		31,879
Income tax expense		15,453		22,791
Net loss		(65,242)		(138,326)
Net loss attributable to noncontrolling interests and redeemable noncontrolling interests		(90,364)		(176,175)
Net income available to common stockholders		$ 25,122		$ 37,849
Basic (in dollars per share)		$ 0.24		$ 0.36
Diluted (in dollars per share)		$ 0.23		$ 0.35
Adoption Impact | Accounting Standards Update 2014-09 and ASC 842
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue: Customer agreements and incentives		$ (7,226)		$ (6,234)
Cost of customer agreements and incentives		(1,825)		(3,548)
Sales and marketing		2,272		3,728
General and administrative		(2)		(15)
Interest expense, net		5,369		10,650
Income tax expense		(4,672)		(6,610)
Net loss		(8,368)		(10,439)
Net loss attributable to noncontrolling interests and redeemable noncontrolling interests		(1,592)		(818)
Net income available to common stockholders		$ (6,776)		$ (9,621)
Basic (in dollars per share)		$ (0.07)		$ (0.09)
Diluted (in dollars per share)		$ (0.06)		$ (0.09)