Income Tax (Tables)

12 Months Ended

Dec. 31, 2017

Pretax earnings (loss) were generated by both domestic and foreign operations as follows (in thousands):

A reconciliation of the expected statutory federal income tax provision to the actual income tax provision is summarized as follows (in thousands):

	Years Ended December 31,
	2017			2016			2015
Expected income taxes benefit at federal statutory rate	$	(16,390	)	$	(19,687	)	$	(16,311	)
State income taxes, net of federal benefit		(13	)		—			—
Permanent items and other		1,311			675			865
Research credits		(2,286	)		(6,800	)		(2,674	)
Unrecognized tax benefits		914			2,720			1,070
Foreign rate differential		87			141			84
Change in tax rate		(25	)		—			3,551
Tax cuts and Jobs Act		27,933			—			—
Change in valuation allowance		(11,531	)		22,902			13,415
Income tax (benefit) expense	$	—		$	(49	)	$	—

Significant components of our deferred tax assets are summarized as follows (in thousands):

	December 31,
	2017			2016
Net operating loss carryforwards	$	27,226		$	33,713
Capitalized research and development expenses		16,218			21,624
Research credits and other state credits		11,229			9,227
Intangible assets		2,210			3,874
Reserve and accruals		2,843			2,711
Valuation allowance		(59,726	)		(71,149	)
Net deferred tax assets	$	—		$	—

The activity related to our unrecognized tax benefits is summarized as follows (in thousands):

	December 31,
	2017			2016		2015
Balance as of beginning of year	$	13,000		$	5,033	$	1,106
Increase (decrease) related to prior year tax positions		(189	)		1,890		2,404
Increase related to current year tax positions		3,747			6,077		1,523
Balance as of end of year	$	16,558		$	13,000	$	5,033