Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Tax Disclosure [Line Items]
Tax Cuts and Jobs Act, percentage of depreciation for certain fixed assets acquired			100.00%
Provisional remeasurement of deferred tax assets and liabilities resulted in an discrete tax benefit		$ 11,500,000
Decrease in provisional remeasurement amount			$ 300,000
Effective tax rate	29.90%		23.10%	41.50%
Provisional income tax benefit due to reduction in Federal corporate tax rate	$ (33,000)		$ 11,203,000
Effective income tax rate excluding impact of net deferred tax liability			34.30%
Unrecognized income tax benefits	$ 0		$ 0
Federal
Income Tax Disclosure [Abstract]
Number of years for examination			4 years
Federal | Tax Year 2017
Income Tax Disclosure [Line Items]
Corporate income tax rate			35.00%
Federal | Tax Year 2018
Income Tax Disclosure [Line Items]
Corporate income tax rate			21.00%
New York
Income Tax Disclosure [Abstract]
Number of years for examination			4 years
Connecticut
Income Tax Disclosure [Abstract]
Number of years for examination			4 years
Pennsylvania
Income Tax Disclosure [Abstract]
Number of years for examination			4 years
New Jersey
Income Tax Disclosure [Abstract]
Number of years for examination			5 years