CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2019		26,547
Beginning balance at Dec. 31, 2019	$ 143,267	$ 8	$ 480,578	$ 1,312	$ (338,631)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		275
Exercise of common stock options	$ 5,426		$ 5,426
Stock Issued During Period, Shares, Warrants Exercised In Period	0	9	0
Vesting of common stock warrants	$ 12,347
Stock-based compensation			$ 12,347
Stock Issued During Period, Value, Restricted Stock Award, Gross		$ 0	0
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures		416
Settlement of restricted stock (in shares)		0
Stock Issued During Period, Value, Employee Stock Purchase Plan	1,312	$ 28	1,312
Other comprehensive loss	1,402			1,402
Net loss	(33,289)				(33,289)
Ending balance (in shares) at Jun. 30, 2020		27,275
Ending balance at Jun. 30, 2020	130,465	$ 8	499,663	2,714	(371,920)
Beginning balance (in shares) at Mar. 31, 2020		26,824
Beginning balance at Mar. 31, 2020	138,358	$ 8	487,903	2,609	(352,162)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		114
Exercise of common stock options	2,281		2,281
Vesting of common stock warrants	8,167
Stock-based compensation			8,167
Stock Issued During Period, Value, Restricted Stock Award, Gross		$ 0	0
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures		309
Settlement of restricted stock (in shares)
Stock Issued During Period, Value, Employee Stock Purchase Plan	1,312	$ 28	1,312
Other comprehensive loss	105			105
Net loss	(19,758)				(19,758)
Ending balance (in shares) at Jun. 30, 2020		27,275
Ending balance at Jun. 30, 2020	130,465	$ 8	499,663	2,714	(371,920)
Beginning balance (in shares) at Dec. 31, 2020		27,861
Beginning balance at Dec. 31, 2020	$ 157,192	$ 8	551,429	(192)	(394,053)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)	80	84
Exercise of common stock options	$ 1,456		1,456
Stock-based compensation	20,937		20,937
Settlement of restricted stock (in shares)		303
Issuance of common stock (in shares)		3,850
Issuance of common stock	484,049		484,049
Stock Issued During Period, Value, Employee Stock Purchase Plan	1,637	$ 21	1,637
Common stock purchase consideration for the acquisition of Dosh	117,349		117,349
Fair value of assumed Dosh options attributable to pre-combination service	3,593		3,593
Other comprehensive loss	(460)			(460)
Net loss	(72,201)				(72,201)
Ending balance (in shares) at Jun. 30, 2021		33,023
Ending balance at Jun. 30, 2021	714,392	$ 8	1,181,290	(652)	(466,254)
Beginning balance (in shares) at Mar. 31, 2021		31,770
Beginning balance at Mar. 31, 2021	744,892	$ 8	1,164,320	(488)	(418,948)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		53
Exercise of common stock options	951		951
Stock-based compensation	13,542		13,542
Settlement of restricted stock (in shares)		275
Issuance of common stock (in shares)		0
Issuance of common stock	0		0
Stock Issued During Period, Value, Employee Stock Purchase Plan	1,637	$ 21	1,637
Common stock purchase consideration for the acquisition of Dosh	0		0
Fair value of assumed Dosh options attributable to pre-combination service	840		840
Other comprehensive loss	(164)			(164)
Net loss	(47,306)				(47,306)
Ending balance (in shares) at Jun. 30, 2021		33,023
Ending balance at Jun. 30, 2021	$ 714,392	$ 8	$ 1,181,290	$ (652)	$ (466,254)