Financial Derivatives (Futures) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Fair Value		$ (1,143)	$ (9,074)
Financial derivatives–assets, at fair value-		13,028	15,479
Derivative Liability		$ 14,171	24,553
Futures
Derivative [Line Items]
Remaining Years to Maturity		3 months 3 days
Financial derivatives–assets, at fair value-		$ 659	2
Derivative Liability		155	376
Short | Futures
Derivative [Line Items]
Notional Amount		176,600	176,600
Fair Value		504	(374)
Remaining Years to Maturity	2 months 26 days
Financial Derivatives - Liabilities | Short | U.S. Treasury futures
Derivative [Line Items]
Notional Amount		$ 34,300	178,200
Remaining Years to Maturity	2 months 26 days	2 months 23 days
Derivative Liability		$ (155)	(367)
Financial Derivatives - Liabilities | Long | U.S. Treasury futures
Derivative [Line Items]
Notional Amount		$ 0	1,900
Remaining Years to Maturity	2 months 19 days	0 years
Derivative Liability		$ 0	(9)
Financial Derivatives - Assets | Short | U.S. Treasury futures
Derivative [Line Items]
Notional Amount		$ 144,200	300
Remaining Years to Maturity	2 months 19 days	3 months 3 days
Financial derivatives–assets, at fair value-		$ 529	2
Financial Derivatives - Assets | Long | U.S. Treasury futures
Derivative [Line Items]
Notional Amount		$ 1,900	0
Remaining Years to Maturity		2 months 23 days
Financial derivatives–assets, at fair value-		$ 130	$ 0