Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

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, 2018, 2017 and 2016, was as follows (in thousands):

	2018			2017			2016
Loss before income taxes:
U.S.	$	(58,048	)	$	(57,925	)	$	(63,246	)
Foreign		713			1,227			515
Loss before income taxes	$	(57,335	)	$	(56,698	)	$	(62,731	)

Provision Benefit for Income Taxes

The provision for income taxes for the years ended December 31, 2018, 2017 and 2016, was as follows (in thousands):

	2018		2017		2016
Provision for income taxes:
Current:
Foreign	$	225	$	181	$	147
Federal		—		—		—
State		—		—		—
Total current		225		181		147
Deferred:
Foreign		—		—		—
Federal		3		3,659		28
State		1		47		—
Total deferred		4		3,706		28
Provision for income taxes	$	229	$	3,887	$	175

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, 2018, 2017 and 2016, was as follows (in thousands):

	2018			2017			2016
Federal statutory tax	$	(12,040	)	$	(19,277	)	$	(21,329	)
Tax Act revaluation of deferred taxes		—			81,923			—
Tax Act deemed income inclusion		—			1,083			—
Federal research credits		(1,390	)		(1,000	)		(809	)
State research credits		(655	)		(628	)		(449	)
Expiration of federal carryovers		4,154			—			—
Expiration of state carryovers		1,344			1,475			1,193
Change in valuation allowance		9,913			(59,462	)		3,940
Compensation related items		(361	)		1,382			484
State taxes		(1,141	)		(803	)		(990	)
Revision to prior year items		—			—			17,200
Other		405			(806	)		935
Provision for income taxes	$	229		$	3,887		$	175

Significant Components of Deferred Tax Assets and Liabilities

The significant components of the Company’s deferred tax assets and liabilities at December 31, 2018 and 2017, were as follows (in thousands):

	December 31,
	2018			2017
Deferred tax assets:
Net operating loss carryforwards	$	125,016		$	117,028
Research and development credit carryforwards		26,705			25,061
Capitalized research and development		15,293			17,195
Compensation related items		8,310			7,011
Other		4,013			3,116
Total deferred tax assets		179,337			169,411
Valuation allowance		(179,245	)		(169,332	)
Net deferred tax assets	$	92		$	79
Deferred tax liabilities:
Amortization of goodwill	$	127		$	111
Total deferred tax liabilities	$	127		$	111

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		2019-2021		2022-2028		2029-2038		Expiration
Federal losses carryovers	$	571,992	$	66,880	$	171,270	$	273,585	$	60,257
California loss carryovers		59,752		—		—		59,752		—
Federal research credits		18,631		5,269		7,626		5,736		—
California research credits		10,220		—		—		—		10,220
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,
	2018			2017
Unrecognized tax benefits at beginning of period	$	11,062		$	10,836
Decreases related to expired carryforwards		(401	)		—
Increases related to prior year tax positions		—			19
Increases related to current year tax positions		402			207
Unrecognized tax benefits at end of period	$	11,063		$	11,062