Derivative Financial Instruments - Summary of Outstanding Forward Foreign Currency Contracts by Currency (Details) - Foreign Currency Forward Contracts - Not Designated as Hedging Instrument € in Thousands, £ in Thousands, $ in Thousands, $ in Thousands	Sep. 30, 2020 GBP (£)	Sep. 30, 2020 SGD ($)	Sep. 30, 2020 EUR (€)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 GBP (£)	Sep. 30, 2019 SGD ($)	Sep. 30, 2019 EUR (€)	Sep. 30, 2019 USD ($)
Foreign Exchange Contracts To Sell European Euro for US Dollar | Short
Derivative [Line Items]
Contract amount of forward foreign currency contracts			€ 15,000	$ 17,656			€ 10,800	$ 11,723
Fair value of forward foreign currency contracts to sell and buy foreign currency				0				0
Foreign Exchange Contracts To Purchase British Pounds With US Dollars | Long
Derivative [Line Items]
Contract amount of forward foreign currency contracts	£ 16,555			21,300	£ 5,200			6,400
Fair value of forward foreign currency contracts to sell and buy foreign currency				0				0
Foreign Exchange Contracts To Purchase Singapore Dollars With United States Dollars | Long
Derivative [Line Items]
Contract amount of forward foreign currency contracts		$ 7,815		5,700		$ 5,798		4,200
Fair value of forward foreign currency contracts to sell and buy foreign currency				$ 0				$ 0