Leases - Additional Information (Detail) $ in Thousands	3 Months Ended			6 Months Ended
	Mar. 31, 2024 USD ($) AirCraft	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($) AirCraft	Mar. 31, 2024 USD ($) AirCraft	Mar. 31, 2023 USD ($)
Lessee, Lease, Description [Line Items]
Number of leased aircraft	33			33
Aggregate rental expense under all operating aircraft, equipment and facility leases | $	$ 4,595	$ 3,785		$ 12,565	$ 10,694
Weighted average remaining lease term Operating leases	6 years 4 months 24 days			6 years 4 months 24 days
Weighted average discount rate Operating leases	5.90%			5.90%
RASPRO Aircraft Lease Agreement [Member]
Lessee, Lease, Description [Line Items]
Number of aircraft lease terminated			15
Buyout pricing | $			$ 25,000
RASPRO Aircraft Lease Agreement [Member] | CRJ-900 Aircraft [Member]
Lessee, Lease, Description [Line Items]
Number of leased aircraft	15			15