Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 22, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Federal statutory rate	21.00%	34.00%	35.00%	34.00%
Decrease of net deferred tax assets	$ 0	$ 7,200,000
Deferred tax assets, valuation allowance	27,317,000	15,395,000
Deferred tax assets, valuation allowance, change in amount	11,900,000	(29,000,000)
Operating loss carry forwards	74,300,000
Tax credit carry forwards	$ 1,100,000
Tax credit carry forwards, year begin to expiration	2032
Unrecognized tax benefits, accrued interest and penalties	$ 0	$ 0
Domestic Tax Authority [Member]
Income Tax Contingency [Line Items]
Operating loss carry forwards	$ 31,400,000
Tax credit carry forwards, year begin to expiration	2037
Operating loss carry forwards, indefinite life	$ 42,900,000
State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Operating loss carry forwards	$ 56,300,000
Operating loss carry forwards, expiry year start	2022
Operating loss carry forwards, expiry year end	2038
Foreign Tax Authority [Member]
Income Tax Contingency [Line Items]
Tax credit carry forwards	$ 200,000
Tax credit carry forwards, year begin to expiration	2037
Earliest Tax Year [Member]
Income Tax Contingency [Line Items]
Open tax year	2015
Latest Tax Year [Member]
Income Tax Contingency [Line Items]
Open tax year	2017