Income Taxes - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended			12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2018
Income Tax Disclosure [Line Items]
Income tax (benefit) provision		$ (176,000)		$ 1,035,000
Discrete tax expense				$ 1,200,000
U.S. federal statutory tax rate	21.00%			35.00%	24.50%
Discrete tax benefit		500,000		$ 200,000
Unrecognized tax benefits excluding interest and penalties that would impact effective tax rate		1,700,000			$ 1,400,000
Undistributed earnings in foreign subsidiaries		$ 0			$ 0
IRS [Member]
Income Tax Disclosure [Line Items]
Income tax examination, year under examination			2016