Income Tax - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended		12 Months Ended
	Mar. 31, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2017
Income Tax [Line Items]
Income tax benefit (expense)		$ 0	$ (540,000)
Reduction of previously recorded valuation allowance		13,400,000
Income tax related to share based compensation windfall settled	$ 600,000
Deferred tax benefit		$ 0	$ 540,000
Federal statutory rate		35.00%
Income taxes paid		$ 0
Scenario, Forecast [Member]
Income Tax [Line Items]
Percentage of annual effective income tax rate				0.00%