Consolidated Statements of Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Revenue from Related Parties	$ 3,773	$ 345	$ 5,020	$ 509
Revenues (includes related party revenue of $3,773 and $345 for the three months ended June 30, 2020 and 2019, respectively, and $5,020 and $509 for the six months ended June 30, 2020 and 2019, respectively)	62,685	88,075	146,211	173,657
Costs and operating expenses:
Cost of revenue (exclusive of depreciation and amortization presented separately below; includes related party cost of revenue of $139 and $289 for the three months ended June 30, 2020 and 2019, respectively, and $424 and $423 for the six months ended June 30, 2020 and 2019, respectively)	6,859	8,332	14,080	17,268
Sales and marketing (includes related party expenses of $0 and $5,749 for the three months ended June 30, 2020 and 2019, respectively, and $1,959 and $11,222 for the six months ended June 30, 2020 and 2019, respectively)	33,476	60,233	80,051	114,971
Technology and development	13,103	16,045	25,319	31,699
General and administrative	13,520	21,382	25,832	36,486
Depreciation and amortization	6,425	6,767	12,696	13,182
Goodwill impairment	0	0	10,187	0
Total costs and operating expenses	73,383	112,759	168,165	213,606
Loss from operations	(10,698)	(24,684)	(21,954)	(39,949)
Interest income	72	966	605	1,967
Loss from equity method investment	(507)	(273)	(889)	(273)
Loss before income taxes	(11,133)	(23,991)	(22,238)	(38,255)
Provision for (benefit from) income taxes	109	69	(327)	170
Net loss	$ (11,242)	$ (24,060)	$ (21,911)	$ (38,425)
Net loss per share attributable to common stockholders:
Net loss per share, basic and diluted (in dollars per share)	$ (0.10)	$ (0.23)	$ (0.20)	$ (0.37)
Weighted average common shares outstanding, basic and diluted (in shares)	107,535	105,485	107,279	105,139
Other comprehensive loss:
Comprehensive loss	$ (11,242)	$ (24,060)	$ (21,911)	$ (38,425)