Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Schedule of reconciliation of the statutory U.S. federal rate to the Company's effective tax rate

A reconciliation of the statutory U.S. federal rate to the Company's effective tax rate is as follows:

	Years ended December 31,
	2018		2017		2016
Percent of pre-tax income:
U.S. federal statutory income tax rate	21.0	%	35.0	%	35.0	%
State taxes, net of federal benefit	18.5	%	14.6	%	2.8	%
Permanent items	4.0	%	4.0	%	(1.4	)%
Remeasurement of deferred tax assets	—	%	49.9	%	—	%
Impact of state rate changes	(0.2	)%	(27.9	)%	(11.0	)%
Research and development credit	(2.4	)%	—	%	1.9	%
Alternative minimum tax credit	—	%	(1.3	)%	1.1	%
Change in valuation allowance	(42.6	)%	(78.6	)%	(28.2	)%
Effective income tax rate	(1.7	)%	(4.3	)%	0.2	%

Schedule of components of income tax (benefit) expense

The components of income tax benefit are as follows:

	Years ended December 31,
	2018			2017			2016
Current:
Federal	$	—		$	173		$	(23,393	)
State	(1,063		)	(1,356		)	21
Deferred:
Federal	—			(3,529		)	22,966
State	—			—			—
Income tax benefit	$	(1,063	)	$	(4,712	)	$	(406	)

Schedule of significant components of the Company's deferred tax assets (liabilities)

Significant components of the Company's deferred tax assets (liabilities) for 2018 and 2017 consist of the following:

	As of December 31,
	2018			2017
Deferred tax assets (liabilities)
Deferred revenue	$	—		$	40,961
License and technology payments	7,221			8,222
Share-based compensation	20,342			17,599
Accrued expenses	371			608
Depreciation	(28		)	81
Federal and state net operating loss carryforwards	88,766			76,309
Research and development credits	5,933			3,782
Other	5			3,534
Deferred income tax assets	122,610			151,096
Valuation allowance	(122,610		)	(147,567		)
Net deferred tax assets	$	—		$	3,529

Schedule of position with respect to uncertain tax positions

The Company's position with respect to uncertain tax positions is set forth below:

Opening balance	$	16,881
Gross amount of increases in unrecognized tax benefits during the period - current year provisions	—
Gross amount of increases in unrecognized tax benefits during the period - prior year provisions	17
Gross amount of decreases in unrecognized tax benefits during the period - other	(1,413		)
Decreases due to settlement with tax authorities during the period	(1,502		)
Reduction of unrecognized tax benefits due to expiration of the state of limitations during the period	—
Closing Balance	$	13,983