Income Taxes - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Federal and State
Income Taxes [Line Items]
Net operating loss carryforwards	$ 61,000,000
US Federal
Income Taxes [Line Items]
Current income tax expense benefit	0	$ 0
Deferred income tax expense benefit	$ 0	$ 0