Financial Derivatives (Schedule of Derivative Activity) (Details) - USD ($) $ in Thousands	6 Months Ended	9 Months Ended
	Jun. 30, 2023	Sep. 30, 2022
Interest rate swaps
Derivative [Line Items]
Average Monthly Notional	$ 4,132,339	$ 3,292,243
TBA securities
Derivative [Line Items]
Average Monthly Notional	684,485	796,003
Credit default swaps
Derivative [Line Items]
Average Monthly Notional	306,397	130,819
Total return swaps
Derivative [Line Items]
Average Monthly Notional	0	688
Futures
Derivative [Line Items]
Average Monthly Notional	218,886	186,446
Options
Derivative [Line Items]
Average Monthly Notional	0	13,846
Forwards
Derivative [Line Items]
Average Monthly Notional	11,873	13,676
Warrants
Derivative [Line Items]
Average Monthly Notional	$ 3,115	$ 3,378