Income Taxes - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended				6 Months Ended
	Dec. 31, 2017	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
Income Tax Disclosure [Line Items]
Income tax benefit		$ 162,000		$ 1,220,000		$ 338,000	$ 185,000
Discrete tax expense							$ 1,200,000
U.S. federal statutory tax rate	21.00%	21.00%		24.50%	35.00%	21.00%	24.50%
Discrete tax benefit				$ 200,000		$ 500,000	$ 400,000
Unrecognized tax benefits excluding interest and penalties that would impact effective tax rate		$ 1,700,000				1,700,000		$ 1,400,000
Undistributed earnings in foreign subsidiaries		0				$ 0		$ 0
IRS [Member]
Income Tax Disclosure [Line Items]
Income tax examination, year under examination			2016
Maximum [Member]
Income Tax Disclosure [Line Items]
Discrete tax benefit		$ 100,000