Derivative Financial Instruments - Notional amounts (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Interest rate swap contract | New Agreement | Derivatives designated as hedging instruments
Derivative [Line Items]
Derivative, notional amount	$ 555,210	$ 0
Interest rate swap contract | Terminated Agreement | Derivatives designated as hedging instruments
Derivative [Line Items]
Derivative, notional amount	0	571,000
Foreign exchange contracts | Buy | Derivatives not designated as hedging instruments
Derivative [Line Items]
Derivative, notional amount	4,225	8,054
Foreign exchange contracts | Sell | Derivatives not designated as hedging instruments
Derivative [Line Items]
Derivative, notional amount	$ 23,235	$ 25,105