Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Line Items]
Effective tax rate	29.60%	(5.30%)
Provisional remeasurement of deferred tax liabilities resulted in an discrete tax benefit	$ 0	$ 11,500,000
Effective income tax rate excluding impact of net deferred tax liability		34.70%
Unrecognized income tax benefits	$ 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