Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Reconciliation of Federal Statutory Income Tax Rate

Reconciliation of the Federal statutory income tax rate of 34% to the effective rate is as follows:

	2017			2016			2015
Federal statutory income (benefit) tax rate		(34.00	%)		34.00	%		34.00	%
2017 Tax Act, net deferred tax remeasurement		(626.73	)		—			—
State taxes, net of federal benefit		(2.01	)		2.88			3.45
Stock compensation		(5.18	)		(0.61	)		—
Permanent differences-other		(13.39	)		(1.00	)		(4.66	)
North Carolina tax rate change		(32.75	)		—			—
Research and development (“R&D”) credit		5.54			0.98			0.95
Valuation release for bargain purchase gain		(302.23	)		—			—
Other		(1.36	)		(0.47	)		0.64
Decrease (increase) in valuation allowance		709.88			(35.78	)		(34.38	)
		(302.23	%)		0.00	%		0.00	%

Significant Components of Deferred Tax Assets and Liabilities

The tax effects of temporary differences and net operating losses that give rise to significant components of deferred tax assets and liabilities consist of the following:

	December 31,
Deferred tax assets (liabilities)	2017			2016
Deferred revenue	$	—		$	7,377
Basis difference in equipment		(587	)		(1,084	)
Basis difference in intangibles		(8,288	)		1,201
Accrued liabilities and other		654			550
R&D credit		11,882			11,589
AMT credit		79			79
Stock options		6,115			5,697
Net operating loss carry-forward		61,660			83,621
		71,515			109,030
Less: valuation allowance		(71,515	)		(109,030	)
	$	—		$	—