Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Taxes

Summary of Components of the Provision for Income Taxes

The components of the provision for income taxes for the year ended December 31, 2018,  2017 and 2016, are as follows (in thousands):

	Year Ended December 31,
	2018		2017		2016
Current:
Federal	$	—	$	—	$	—
State		4		5		—
Foreign		—		1,204		—
Total current		4		1,209		—
Deferred:
Federal				(30)		—
State		—		—		—
Foreign		—		—		—
Total deferred		—		(30)		—
Provision for (benefit from) income taxes	$	4	$	1,179	$	—

Reconciliation of Statutory Federal Income Tax Rate to the Company's Effective Tax Rate

	December 31,
	2018		2017		2016
Income tax at the federal statutory rate	21.0	%	35.0	%	35.0	%
State taxes, net of federal benefit	0.6		0.5		0.3
Net impact related to foreign subsidiary	—		(1.2)		—
Change in valuation allowance	(22.5)		19.9		(36.2)
Impact of tax reform rate change	—		(56.4)		—
Tax credits	1.4		1.0		0.3
Stock Based Compensation	(1.2)		(0.8)		0.1
Other	0.7		0.1		0.5
Income tax provision	—	%	(1.9)	%	—	%

Significant Components of the Company's Deferred Tax Assets

	December 31,
	2018		2017
	(in thousands)
Deferred tax assets:
Fixed assets and intangibles	$	38,376	$	30,804
Net operating loss carryforwards		31,621		22,355
Tax credits		8,200		5,209
Stock-based compensation		3,763		3,159
Other		888		754
Gross deferred tax assets		82,848		62,281
Valuation allowance		(81,645)		(61,911)
Deferred tax assets net of valuation allowance		1,203		370
Deferred tax liabilities
Adoption of New Accounting Standards		(1,054)		—
Other		(149)		(370)
Net deferred tax assets	$	—	$	—

Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits

	December 31,
	2018		2017		2016
	(in thousands)
Balance at beginning of year	$	20,734	$	3,892	$	3,298
Additions (subtractions) based on tax positions related to prior year		1,634		16,103		45
Additions based on tax positions related to current year		684		739		549
Balance at end of year	$	23,052	$	20,734	$	3,892