Income Taxes - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended			6 Months Ended		12 Months Ended
	Dec. 31, 2017	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2018
Income Tax Disclosure [Line Items]
Income tax (benefit) provision		$ (1,220,000)		$ 1,055,000	$ (185,000)	$ 2,782,000
Discrete tax expense					$ 1,200,000
U.S. federal statutory tax rate	21.00%	24.50%		35.00%	24.50%	35.00%
Discrete tax benefit (expense)		$ 200,000			$ 400,000	$ (300,000)
Unrecognized tax benefits excluding interest and penalties that would impact effective tax rate		1,500,000	$ 1,200,000		1,500,000
Undistributed earnings in foreign subsidiaries		$ 0	$ 0		$ 0
IRS [Member]
Income Tax Disclosure [Line Items]
Income tax examination, year under examination			2016
Expected Statutory Income Tax Rate [Member]
Income Tax Disclosure [Line Items]
U.S. federal statutory tax rate							24.50%