Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income (Loss) Before Provision for Income Taxes

Income (loss) before provision for income taxes includes the following components (in thousands):

	Year Ended December 31,
	2018		2017			2016
Domestic	$	680,423	$	(97,938	)	$	(155,375	)
Foreign		2,302		1,862			2,727
Income (loss) before provision for income taxes	$	682,725	$	(96,076	)	$	(152,648	)

Provision for Income Taxes

The provision for income taxes consists of the following (in thousands):

	Year Ended December 31,
	2018		2017		2016
Current:
Federal	$	—	$	—	$	—
State		699		1		(1	)
Foreign		620		580		992
Total Current		1,319		581		991
Deferred:
Federal		—		—		—
State		—		—		—
Foreign		93		35		(115	)
Total Deferred		93		35		(115	)
Provision for income taxes	$	1,412	$	616	$	876

Income Tax Provision Related to Continuing Operations

Income tax provision related to continuing operations differs from the amount computed by applying the statutory income tax rate of 21% for 2018 and 35% for 2017 and 2016 to pretax income (loss) as follows (in thousands):

	Year Ended December 31,
	2018			2017			2016
Income tax expense (benefit) at federal statutory rate	$	143,372		$	(33,627	)	$	(53,427	)
Non-cash interest expense on liability related to sale of    future royalties		4,451			6,604			6,899
Non-deductible officers' compensation		3,182			2,547			220
Tax law changes		45			248,155			—
Stock-based compensation		(66,716	)		(20,665	)		528
Change in valuation allowance		(46,885	)		(186,124	)		51,981
Research credits		(17,295	)		(8,038	)		(4,543	)
Premium on equity issuance		(12,551	)		—			—
Sale of future royalties		(6,995	)		(8,236	)		—
Other		804			—			(782	)
Provision for income taxes	$	1,412		$	616		$	876

Significant Components of Deferred Tax Assets and Liabilities

We remeasured certain deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future, which includes the change in the federal rate to 21% as of December 31, 2017. Significant components of our deferred tax assets for federal and state income taxes are as follows (in thousands):

	December 31,
	2018			2017
Deferred tax assets:
Net operating loss carryforwards	$	300,693		$	364,864
Research and other credits		116,955			94,103
Stock-based compensation		21,518			14,552
Capitalized research expenses		8,072			5,497
Reserves and accruals		8,066			5,659
Deferred revenue		4,467			3,796
Property, plant and equipment		2,124			6,848
Other		(1,270	)		1,156
Deferred tax assets before valuation allowance		460,625			496,475
Valuation allowance for deferred tax assets		(460,455	)		(496,191	)
Total deferred tax assets		170			284
Total deferred tax liabilities		—			—
Net deferred tax assets	$	170		$	284

Unrecognized Tax Benefits

We have the following activity relating to unrecognized tax benefits (in thousands):

	December 31,
	2018		2017			2016
Beginning balance	$	20,483	$	18,413		$	17,384
Tax positions related to current year
Additions:
Federal		2,019		1,206			530
State		3,645		1,666			499
Reductions		—		—			—
Tax positions related to prior year
Additions:
Federal		669		—			—
State		603		—			—
Foreign		—		—			—
Reductions				(802	)		—
Settlements		—		—			—
Lapses in statute of limitations		—		—			—
Ending balance	$	27,419	$	20,483		$	18,413