Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Components of Loss before Income Taxes

The components of the Company’s loss before income taxes were as follows:

	Years Ended December 31,
	2018			2017			2016
	(in thousands)
Domestic	$	(52,755	)	$	(39,370	)	$	(34,258	)
Foreign		4,318			4,120			4,103
Total loss before income taxes	$	(48,437	)	$	(35,250	)	$	(30,155	)

Components of Provision for Income Taxes

The components of the provision for income taxes are as follows (in thousands):

	Years Ended December 31,
	2018			2017		2016
Current:
Federal	$	—		$	—	$	—
State		220			170		181
Foreign		1,477			1,238		1,442
Total current		1,697			1,408		1,623
Deferred:
Federal		—			—		—
State		—			—		—
Foreign		(929	)		—		—
Total deferred		(929	)		—		—
Total provision for income taxes	$	768		$	1,408	$	1,623

Income Tax Expense by Applying Statutory Federal Income Tax Rate

Income tax expense differs from the amount computed by applying the statutory federal income tax rate as follows:

	Years Ended December 31,
	2018			2017			2016
Tax at statutory federal rate		21.0	%		34.0	%		34.0	%
State tax, net of federal benefit		(0.4	)%		(0.4	)%		(0.4	)%
Other		(4.9	)%		(4.4	)%		(3.7	)%
Foreign rate differential		(1.0	)%		0.5	%		(0.2	)%
Tax credits		2.8	%		4.5	%		3.2	%
Excess tax benefits related to stock-based compensation		2.0	%		21.5	%		—	%
Effect of Tax Cuts and Jobs Act of 2017		—	%		(121.1	)%		—	%
Change in valuation allowance		(21.2	)%		61.4	%		(38.4	)%
Total		(1.7	)%		(4.0	)%		(5.5	)%

Tax Effects of Temporary Differences and Carryforwards that Give Rise to Significant Portions of Deferred Tax Assets

The tax effects of temporary differences and carryforwards that give rise to significant portions of deferred tax assets are as follows:

	December 31,
	2018			2017
	(in thousands)
Net operating loss carryforwards	$	68,552		$	60,999
Tax credits		12,451			10,198
Depreciation		339			133
Stock-based compensation		10,770			6,983
Accruals and reserves		7,507			7,280
Other		2,057			2,525
Deferred tax assets		101,676			88,118
Other		—			—
Deferred tax liabilities		—			—
Valuation allowance		(100,747	)		(88,118	)
Net deferred tax assets	$	929		$	—

Summary of Unrecognized Tax Benefits

The following table summarizes the activity related to UTBs (in thousands):

Balance at December 31, 2015	$	3,844
Increases related to current year tax provisions		1,059
Decreases related to prior year tax provisions		(1,519	)
Balance at December 31, 2016		3,384
Increases related to current year tax provisions		790
Increases related to prior year tax provisions		193
Decreases related to prior year tax provisions		(134	)
Balance at December 31, 2017		4,233
Increases related to current year tax provisions		893
Increases related to prior year tax provisions		80
Decreases related to prior year tax provisions		(6	)
Balance at December 31, 2018	$	5,200