Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

United States and Foreign Components of Consolidated Loss Before Income Taxes

U.S and foreign components of consolidated loss before income taxes for the years ended December 31, 2020, 2019 and 2018, was as follows (in thousands):

	2020			2019			2018
Loss before income taxes:
U.S.	$	(61,246	)	$	(71,946	)	$	(58,048	)
Foreign		1,673			965			713
Loss before income taxes	$	(59,573	)	$	(70,981	)	$	(57,335	)

Provision Benefit for Income Taxes

The provision for income taxes for the years ended December 31, 2020, 2019 and 2018, was as follows (in thousands):

	2020		2019		2018
Provision for income taxes:
Current:
Foreign	$	274	$	255	$	225
Federal		—		—		—
State		—		2		—
Total current		274		257		225
Deferred:
Foreign		—		—		—
Federal		6		4		3
State		4		2		1
Total deferred		10		6		4
Provision for income taxes	$	284	$	263	$	229

Difference Between Provision for Income Taxes and Amounts Computed by Applying Federal Statutory Income Tax Rate to Loss before Taxes

The difference between the provision for income taxes and the amount computed by applying the federal statutory income tax rate to loss before taxes for the years ended December 31, 2020, 2019 and 2018, was as follows (in thousands):

	2020			2019			2018
Federal statutory tax	$	(12,510	)	$	(14,906	)	$	(12,040	)
Federal research credits		(1,630	)		(1,857	)		(1,390	)
State research credits		(749	)		(821	)		(655	)
Expiration of federal carryovers		9,200			5,472			4,154
Expiration of state carryovers		—			—			1,344
Change in valuation allowance		6,738			13,059			9,913
Compensation related items		978			158			(361	)
State taxes		(1,921	)		(1,111	)		(1,141	)
Other		178			269			405
Provision for income taxes	$	284		$	263		$	229

Significant Components of Deferred Tax Assets and Liabilities

The significant components of the Company’s deferred tax assets and liabilities at December 31, 2020, 2019 and 2018, were as follows (in thousands):

Gross Amounts and Dates of Expiration of Tax Credits and Carryovers

The Company's tax losses and credits are subject to varying carryforward periods. The gross amounts and dates of expiration of the significant carryforwards are as follows:

			Expires		Expires		Expires		No
	Total		2021-2023		2024-2030		2031-2040		Expiration
Federal losses carryovers	$	638,103	$	55,587	$	190,581	$	209,368	$	182,567
California loss carryovers		75,407		—		28,779		46,628		—
Federal research credits		19,249		7,786		2,248		9,215		—
California research credits		12,207		—		—		—		12,207
Federal foreign tax credits		610		—		610		—		—

Reconciliation of Unrecognized Tax Benefits

The following is a tabular reconciliation of the total amounts of unrecognized tax benefits (in thousands):

	December 31,			December 31,
	2020			2019
Unrecognized tax benefits at beginning of period	$	10,842		$	11,063
Decreases related to expired carryforwards		(1,171	)		(729	)
Increases related to current year tax positions		439			508
Unrecognized tax benefits at end of period	$	10,110		$	10,842