Derivatives and Hedging Activities - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Derivative [Line Items]
Investment income	$ 255,346	$ 150,838	$ 488,765	$ 301,278
Interest Rate Swap
Derivative [Line Items]
Investment income			$ 26	$ 0
Interest Rate Swap | Minimum
Derivative [Line Items]
Derivative, maturities			1 year
Interest Rate Swap | Maximum
Derivative [Line Items]
Derivative, maturities			7 years
Interest Rate Swap | Weighted average
Derivative [Line Items]
Derivative, maturities			6 years