CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - 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	$ 28,222	$ 48,730	$ 73,731	$ 84,718
Costs and expenses:
FI Share and other third-party costs	16,811	27,620	42,949	46,624
Delivery costs	3,499	3,370	6,905	6,616
Sales and marketing expense	10,405	11,047	21,373	20,384
Research and development expense	3,966	2,782	7,817	5,723
General and administration expense	11,734	8,340	22,478	15,340
Depreciation and amortization expense	1,545	1,053	3,876	2,014
Total costs and expenses	47,960	54,212	105,398	96,701
Operating loss	(19,738)	(5,482)	(31,667)	(11,983)
Other expense:
Interest (expense) income, net	(10)	(338)	274	(642)
Foreign currency loss	(10)	(690)	(1,896)	(199)
Total other expense	(20)	(1,028)	(1,622)	(841)
Loss before income taxes	(19,758)	(6,510)	(33,289)	(12,824)
Income Tax Expense (Benefit)	0		0	0
Net loss	(19,758)	(6,510)	(33,289)	(12,824)
Net loss attributable to common stockholders	$ (19,758)	$ (6,510)	$ (33,289)	$ (12,824)
Net loss per share attributable to common stockholders, basic and diluted (in USD per share)	$ (0.73)	$ (0.29)	$ (1.24)	$ (0.57)
Weighted-average common shares outstanding, basic and diluted (in shares)	27,072	22,731	26,898	22,618