Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Schedule of Income before Income Tax, Domestic and Foreign

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

	Year Ended December 31,
	2020		2019		2018
Domestic	$	(445,370)	$	(441,494)	$	680,423
Foreign	1,423		1,440		2,302
Income (loss) before provision for income taxes	$	(443,947)	$	(440,054)	$	682,725

Provision for Income Taxes

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

	Year Ended December 31,
	2020		2019		2018
Current:
Federal	$	—	$	—	$	—
State	165		139		699
Foreign	364		495		620
Total Current	529		634		1,319
Deferred:
Federal	—		—		—
State	—		—		—
Foreign	(36)		(21)		93
Total Deferred	(36)		(21)		93
Provision for income taxes	$	493	$	613	$	1,412

Income Tax Provision Related to Continuing Operations

Our income tax provision related to continuing operations differs from the amount computed by applying the statutory income tax rate of 21% for the years ended December 31, 2020, 2019 and 2018 to pretax income (loss) as follows (in thousands):

	Year Ended December 31,
	2020		2019		2018
Income tax expense (benefit) at federal statutory rate	$	(93,229)	$	(92,411)	$	143,372
Research credits	(3,081)		(10,511)		(17,295)
Premium on equity issuance	—		—		(12,551)
Change in valuation allowance	87,060		104,440		(46,885)
Stock-based compensation	7,929		(672)		(66,716)
Non-cash royalty revenue related to sale of future royalties	(7,967)		(7,624)		(6,995)
Non-cash interest expense on liability related to sale of future royalties	6,356		5,259		4,451
Other	3,425		2,132		4,031
Provision for income taxes	$	493	$	613	$	1,412

Significant Components of Deferred Tax Assets and Liabilities

We measure deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future. Significant components of our deferred tax assets for federal and state income taxes are as follows (in thousands):

	December 31,
	2020		2019
Deferred tax assets:
Net operating loss carryforwards	$	456,284	$	399,361
Research and other credits	132,994		128,015
Operating lease liabilities	35,672		36,907
Liability related to the sale of future royalties	32,737		—
Stock-based compensation	32,517		30,875
Other	11,688		13,568
Deferred tax assets before valuation allowance	701,892		608,726
Valuation allowance for deferred tax assets	(670,103)		(575,087)
Total deferred tax assets	31,789		33,639
Deferred tax liabilities:
Operating lease right-of-use assets	(29,707)		(31,718)
Other	(1,856)		(1,725)
Total deferred tax liabilities	(31,563)		(33,443)
Net deferred tax assets	$	226	$	196

Unrecognized Tax Benefits

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

	Year Ended December 31,
	2020		2019		2018
Beginning balance	$	77,410	$	27,419	$	20,483
Tax positions related to current year:
Additions	2,512		49,858		5,664
Reductions	—		—		—
Tax positions related to prior years:
Additions	193		277		1,272
Reductions	(1,450)		(144)		—
Settlements	—		—		—
Lapses in statute of limitations	—		—		—
Ending balance	$	78,665	$	77,410	$	27,419