Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Reduction in net deferred tax assets to reflect new statutory rate		$ 8,900,000
Tax credit carryforwards	$ 3,300,000
Tax credit carryforwards expiration period	2019
Period of increase in ownership	3 years
Unrealized tax benefits	$ 0	$ 0
Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	73,400,000
Domestic Tax Authority [Member] | Expire in 2022 and 2023 [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	$ 36,300,000
Domestic Tax Authority [Member] | Minimum [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards expiration period	2022
Domestic Tax Authority [Member] | Maximum [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards expiration period	2023
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	$ 9,000,000
US [Member]
Operating Loss Carryforwards [Line Items]
US federal corporate tax rate	21.00%	35.00%