Derivative Financial Instruments - Effect of Derivative Instruments on Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Other Comprehensive Income (Loss)	$ 7,184	$ (23,161)	$ (23,667)
Interest rate swap contract
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Other Comprehensive Income (Loss)	$ 7,184	$ (23,161)	$ (23,667)