Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Revenue	$ 79,893	$ 59,868
Cost of revenue	74,197	53,492
Gross profit	5,696	6,376
Operating expenses:
Technology and development	12,762	9,672
Marketing	13,336	10,459
General and administrative	16,772	14,367
Total operating expenses	42,870	34,498
Loss from operations	(37,174)	(28,122)
Interest income and other income, net:
Interest income	577	43
Other income, net	158	13
Total interest income and other income, net	735	56
Net loss	(36,439)	(28,066)
Accretion of redeemable convertible preferred stock	0	(24,770)
Net loss attributable to common stock—basic	(36,439)	(52,836)
Net loss attributable to common stock—diluted	$ (36,439)	$ (52,836)
Net loss per share attributable to common stock—basic and diluted (in dollars per share)	$ (0.44)	$ (3.58)
Weighted average shares used to compute net loss per share attributable to common stock—basic and diluted (in shares)	82,010,913	14,767,478