Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Taxes

Schedule of effective tax rates differing from U.S. federal statutory rate

	December 31,
	2020				2019				2018
	(in thousands, except percentages)
U.S. federal taxes (benefit) at statutory rate	$	(48,226)	(21.00)	%	$	(25,794)	(21.00)	%	$	(26,800)	(21.00)	%
State tax expense		(10,672)	(4.65)	%		(6,607)	(5.38)	%		(4,468)	(3.50)	%
Research and development credits		(3,964)	(1.73)	%		(1,645)	(1.34)	%		(1,164)	(0.91)	%
Stock-based compensation		(23,791)	(10.36)	%		(7,544)	(6.14)	%		(3,148)	(2.47)	%
Change in federal tax rate		—	0.00	%		—	0.00	%		—	0.00	%
Mark to market fair value adjustments		—	0.00	%		—	0.00	%		865	0.68	%
Nondeductible settlement for claims		—	0.00	%		—	0.00	%		1	0.00	%
Foreign tax		55	0.02	%		1,612	1.31	%		195	0.15	%
Other nondeductible items		9,776	4.26	%		1,378	1.12	%		690	0.54	%
Change in valuation allowance		76,920	33.50	%		40,599	33.06	%		34,150	26.76	%
Provision for income taxes	$	98	0.04	%	$	1,999	1.63	%	$	321	0.25	%

Schedule of tax effects of temporary differences that give rise to significant portions of the deferred tax assets

	December 31,
	2020		2019
	(in thousands)
Deferred tax assets:
Net operating loss carryforwards	$	177,899	$	124,777
Research and development tax credit carryforwards		24,332		18,189
Reserves and accruals		21,770		10,002
Lease Liabilities		7,123		7,838
Deferred revenue		6,386		3,288
Stock-based compensation		10,673		6,106
Total deferred tax assets before valuation allowance		248,183		170,200
Less: valuation allowance		(222,521)		(163,040)
		25,662		7,160
Deferred tax liabilities:
Convertible debt		(19,143)
Right-of-use lease assets		(6,519)		(7,160)
Net deferred tax assets	$	—	$	—

Schedule of reconciliation of the beginning and ending amount of gross unrecognized tax benefits

	December 31,
	2020		2019		2018
	(in thousands)
Balance at beginning of year	$	8,619	$	7,362	$	5,945
Additions based on tax positions related to the current year		2,889		1,426		1,416
Additions (reductions) for tax positions of prior years		(8)		(169)		1
Balance at end of year	$	11,500	$	8,619	$	7,362