DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Claims Accruals (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Cargo loss and damage claims
Claims accrual	$ 50
Bodily injury and property damage claims
Claims accrual	2,000	$ 1,000
Bodily injury and property damage claims | Skyraider Risk Retention Group Inc. ("SRRG") | Minimum
Claims accrual		1,000
Bodily injury and property damage claims | Skyraider Risk Retention Group Inc. ("SRRG") | Maximum
Claims accrual		$ 2,000
Workers' compensation claims
Claims accrual	500
Employee medical expenses
Claims accrual	$ 250