Income Taxes - Differences Between United States Federal Income Tax Rate and Effective Income Tax Rate (Detail)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Statutory tax (benefit) expense	21.00%	35.00%
Increase (decrease) in taxes resulting from:
Stock-based compensation	(0.00%)	(0.00%)
Nondeductible expenses	1.50%	0.20%
Tax Cuts and Jobs Act impact	(0.00%)	93.20%
Valuation allowance	19.50%	(58.40%)
Effective income tax rate, percent	(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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