Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of Reconciliation of the Company's Effective Tax Rate to the Statutory Federal Income Tax Rate

A reconciliation of the Company’s effective tax rate to the statutory federal income tax rate is as follows:

	Years Ended December 31,
	2019			2018
Federal income tax at statutory federal rate		21.0	%		21.0	%
State taxes		6.2			6.2
Permanent differences		(1.2	)		(0.1	)
Stock-based compensation		—			(0.4	)
Tax Cuts and Jobs Act impact		—			0.1
Tax credits		0.7			2.5
Forfeiture of vested stock options		(24.8	)		—
Other		0.2			—
Change in valuation allowance		4.4			(18.1	)
Total		6.5	%		11.2	%

Schedule of Temporary Differences That Give Rise to Significant Net Deferred Tax Assets

Temporary differences that give rise to significant net deferred tax assets as of December 31, 2019 and 2018 are as follows:

	December 31,
(in thousands)	2019			2018
Deferred tax assets
Net operating losses	$	61,189		$	54,407
Capitalized research and development expenses		564			705
Credit carryforwards		166,459			166,367
Depreciation		—			2,725
Deferred compensation		1,479			6,315
Election out of installment method		820			—
Accrued expenses		—			655
Other temporary differences		1,089			2,423
Installment sale tax basis		15,868			14,881
Total gross deferred tax assets		247,468			248,478
Valuation allowance		(247,468	)		(248,478	)

Schedule of Changes in the Valuation Allowance

The change in the valuation allowance against the deferred tax assets in the years ended December 31, 2019 and 2018 was as follows:

(in thousands)	Balance at Beginning of Period		Additions		Deductions			Balance at End of Period
December 31, 2018		236,067		12,411		—			248,478
December 31, 2019		248,478		—		(1,010	)		247,468