Derivative Instruments, Information of Treasury Futures Agreements (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022
U.S. Treasury Futures [Member]
Treasury Futures Agreements [Abstract]
Fair Value		$ (1,651)	$ 618
U.S. Treasury Futures [Member] | 2 years [Member]
Treasury Futures Agreements [Abstract]
Fair Value		2,090
U.S. Treasury Futures [Member] | 5 years [Member]
Treasury Futures Agreements [Abstract]
Fair Value		4,944
U.S. Treasury Futures [Member] | 10 years [Member]
Treasury Futures Agreements [Abstract]
Fair Value	[1]	$ (8,685)	618
U.S. Treasury Futures Options [Member]
Treasury Futures Agreements [Abstract]
Fair Value			234
U.S. Treasury Futures Options [Member] | 10 years [Member]
Treasury Futures Agreements [Abstract]
Fair Value			234
Ultra Futures Contracts [Member]
Treasury Futures Agreements [Abstract]
Future agreement period		10 years
Long Bond Futures Contracts [Member]
Treasury Futures Agreements [Abstract]
Future agreement period		10 years
Long Positions [Member] | U.S. Treasury Futures [Member]
Treasury Futures Agreements [Abstract]
Net Notional Amount		$ 418,300	0
Long Positions [Member] | U.S. Treasury Futures [Member] | 2 years [Member]
Treasury Futures Agreements [Abstract]
Net Notional Amount		196,800
Long Positions [Member] | U.S. Treasury Futures [Member] | 5 years [Member]
Treasury Futures Agreements [Abstract]
Net Notional Amount		221,500
Long Positions [Member] | U.S. Treasury Futures [Member] | 10 years [Member]
Treasury Futures Agreements [Abstract]
Net Notional Amount	[1]	0	0
Long Positions [Member] | U.S. Treasury Futures Options [Member]
Treasury Futures Agreements [Abstract]
Net Notional Amount			70,000
Long Positions [Member] | U.S. Treasury Futures Options [Member] | 10 years [Member]
Treasury Futures Agreements [Abstract]
Net Notional Amount			70,000
Short Positions [Member] | U.S. Treasury Futures [Member]
Treasury Futures Agreements [Abstract]
Net Notional Amount		144,200	88,700
Short Positions [Member] | U.S. Treasury Futures [Member] | 2 years [Member]
Treasury Futures Agreements [Abstract]
Net Notional Amount		0
Short Positions [Member] | U.S. Treasury Futures [Member] | 5 years [Member]
Treasury Futures Agreements [Abstract]
Net Notional Amount		0
Short Positions [Member] | U.S. Treasury Futures [Member] | 10 years [Member]
Treasury Futures Agreements [Abstract]
Net Notional Amount	[1]	$ 144,200	88,700
Short Positions [Member] | U.S. Treasury Futures Options [Member]
Treasury Futures Agreements [Abstract]
Net Notional Amount			50,000
Short Positions [Member] | U.S. Treasury Futures Options [Member] | 10 years [Member]
Treasury Futures Agreements [Abstract]
Net Notional Amount			$ 50,000

[1] Includes 10-year Ultra futures and Long Bond futures contracts.