Fair Value Measurements and Derivative Instruments - Credit Related Contingent Features (Details) $ in Millions	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($) derivative
Subsequent Event [Line Items]
Number of interest rate derivatives requiring collateral to be posted | derivative		7
Debt instrument, collateral amount		$ 80.0
Interest Contracts
Subsequent Event [Line Items]
Debt instrument, collateral amount		$ 30.5
Scenario, Forecast
Subsequent Event [Line Items]
Debt instrument, collateral amount	$ 60.6