Leases - Summary of Lease Assets and Lease Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Sep. 30, 2022
Assets
ROU operating lease assets	$ 17,532	$ 19,724
Operating Lease Right Of Use Asset Statement Of Financial Position Extensible List	Other assets	Other assets
Finance lease assets	$ 73,080	$ 73,541
Finance Lease Right Of Use Asset Statement Of Financial Position Extensible List	Other assets	Other assets
Total lease assets	$ 90,612	$ 93,265
Current liabilities
Lease liability - operating	$ 4,804	$ 5,223
Operating Lease Liability Current Statement Of Financial Position Extensible List	Accrued expenses and other liabilities	Accrued expenses and other liabilities
Lease liability - finance	$ 2,568	$ 2,366
Finance Lease Liability Current Statement Of Financial Position Extensible List	Accrued expenses and other liabilities	Accrued expenses and other liabilities
Non-Current liabilities
Operating	$ 15,365	$ 17,261
Operating Lease Liability Noncurrent Statement Of Financial Position Extensible List	Other non-current liabilities	Other non-current liabilities
Finance	$ 76,256	$ 75,706
Finance Lease Liability Noncurrent Statement Of Financial Position Extensible List	Other non-current liabilities	Other non-current liabilities
Total lease liabilities	$ 98,993	$ 100,556