Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Taxes [Abstract]

Income (Loss) Before Income Taxes

Income (loss) before income taxes is comprised of (in thousands):

	Year Ended December 31,
	2020			2019		2018
United States	$	(172,702	)	$	344,280	$	(69,576	)
Foreign		2,670			2,489		(6,580	)
Income (loss) before income taxes	$	(170,032	)	$	346,769	$	(76,156	)

Income Tax Expense (Benefit)

Our income tax expense (benefit) was as follows (in thousands):

	Year Ended December 31,
	2020			2019			2018
Current:
Federal	$	(837	)	$	35,861		$	438
State		3,782			14,329			(1,442	)
Foreign		518			413			374
Total current income tax expense (benefit)		3,463			50,603			(630	)
Deferred:
Federal		313,271			(7,096	)		(290,511	)
State		—			—			—
Total deferred income tax benefit		313,271			(7,096	)		(290,511	)
Total income tax expense (benefit)	$	316,734		$	43,507		$	(291,141	)

Reconciliation of Statutory to Effective Tax Rate

Our expense (benefit) for income taxes differs from the amount computed by applying the U.S. federal statutory rate to income (loss) before taxes. The sources and tax effects of the differences are as follows (in thousands):

	Year Ended December 31,
	2020					2019					2018
Pre-tax income (loss)	$	(170,032	)			$	346,769				$	(76,156	)
Statutory rate		(35,707	)	21.0	%		72,822		21.0	%		(15,993	)	21.0	%
State income tax net of federal benefit		(39,230	)	23.1	%		49,119		14.2	%		(2,202	)	2.9	%
Foreign		49		0.0	%		340		0.1	%		1,735		(2.3	)%
Net change in valuation allowance		437,597		(257.4	)%		(37,765	)	(10.9	)%		(277,924	)	364.9	%
Net operating loss expiration		—		0.0	%		—		0.0	%		8,864		(11.6	)%
TEGSEDI licensing gain		—		0.0	%		—		0.0	%		59,583		(78.2	)%
Impact from outside basis differences		—		0.0	%		(16,344	)	(4.7	)%		—		0.0	%
Tax credits		(18,774	)	11.0	%		(22,296	)	(6.4	)%		(73,362	)	96.3	%
Deferred tax true-up		(206	)	0.1	%		646		0.2	%		9,947		(13.1	)%
Tax rate change		(29,131	)	17.1	%		1,811		0.5	%		(1,808	)	2.4	%
Non-deductible compensation		7,931		(4.7	)%		3,361		1.0	%		3,154		(4.1	)%
Other non-deductible items		193		(0.1	)%		329		0.1	%		(569	)	0.7	%
Stock-based compensation		17,435		(10.3	)%		(4,837	)	(1.4	)%		(4,199	)	5.5	%
Foreign-derived intangible income benefit		—		0.0	%		(2,071	)	(0.6	)%		—		0.0	%
Impacts from Akcea Acquisition		(22,032	)	13.0	%		—		—			—		—
Other		(1,391	)	0.8	%		(1,608	)	(0.5	)%		1,633		(2.1	)%
Effective rate	$	316,734		(186.4	)%	$	43,507		12.6	%	$	(291,141	)	382.3	%

Deferred Tax Assets and Liabilities

Significant components of our deferred tax assets and liabilities as of December 31, 2020 and 2019 are as follows (in thousands):

	Year Ended December 31,
	2020			2019
Deferred Tax Assets:
Net operating loss carryovers	$	83,681		$	20,191
Tax credits		245,746			210,455
Deferred revenue		124,452			127,763
Stock-based compensation		80,055			65,703
Intangible and capital assets		98,443			77,861
Other		13,402			12,510
Total deferred tax assets	$	645,779		$	514,483
Deferred Tax Liabilities:
Convertible debt	$	(2,920	)	$	(6,110	)
Fixed assets		(3,611	)		(1,958	)
Other		(5,808	)		(3,884	)
Net deferred tax asset	$	633,440		$	502,531
Valuation allowance		(633,440	)		(196,974	)
Total net deferred tax assets and liabilities	$	—		$	305,557

Gross Unrecognized Tax Benefits

The following table summarizes our gross unrecognized tax benefits (in thousands):

	Year Ended December 31,
	2020			2019			2018
Beginning balance of unrecognized tax benefits	$	69,784		$	68,301		$	78,014
Decrease for prior period tax positions		(24,154	)		(867	)		(12,814	)
Increase for prior period tax positions		7,023			736			—
Increase for current period tax positions		1,510			1,614			3,101
Ending balance of unrecognized tax benefits	$	54,163		$	69,784		$	68,301