Income Taxes - Schedule of Reconciliation between Statutory Federal Income Tax Rate and Effective Tax Rate (Details)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	34.00%	34.00%
State taxes (tax effected)	8.60%	7.10%	8.40%
Non-deductible expenses and other	2.50%	2.00%	(12.90%)
Research and development credits	5.90%	6.00%	17.80%
Tax Act – net deferred tax rate change		(25.10%)
Change in valuation allowance	(38.00%)	(24.00%)	(47.30%)
Total	0.00%	0.00%	0.00%

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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