Financial Derivatives (Futures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Fair Value	$ (9,074)	$ (10,833)
Short | Futures
Derivative [Line Items]
Notional Amount	176,600	30,000
Fair Value	$ (374)	$ 103
Remaining Years to Maturity	2 months 26 days	3 months 10 days
Financial Derivatives - Liabilities | Short | U.S. Treasury futures
Derivative [Line Items]
Notional Amount	$ 178,200	$ 16,000
Fair Value	$ (367)	$ 148
Remaining Years to Maturity	2 months 26 days	2 months 23 days
Financial Derivatives - Liabilities | Short | Eurodollar futures
Derivative [Line Items]
Notional Amount	$ 0	$ 14,000
Fair Value	$ 0	$ (45)
Remaining Years to Maturity	0 years	4 months 2 days
Financial Derivatives - Liabilities | Long | U.S. Treasury futures
Derivative [Line Items]
Notional Amount	$ 1,900	$ 0
Fair Value	$ (9)	$ 0
Remaining Years to Maturity	2 months 19 days	0 years
Financial Derivatives - Assets | Short | U.S. Treasury futures
Derivative [Line Items]
Notional Amount	$ 300	$ 0
Fair Value	$ 2	$ 0
Remaining Years to Maturity	2 months 19 days	0 years