Financial Derivatives (Schedule of Derivative Activity) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Interest rate swaps
Derivative [Line Items]
Average Monthly Notional	$ 1,118,783	$ 731,941
TBA securities
Derivative [Line Items]
Average Monthly Notional	782,346	973,331
Credit default swaps
Derivative [Line Items]
Average Monthly Notional	307,217	399,316
Total return swaps
Derivative [Line Items]
Average Monthly Notional	9,139	39,434
Futures
Derivative [Line Items]
Average Monthly Notional	132,829	167,708
Options
Derivative [Line Items]
Average Monthly Notional	2,786	19,825
Forwards
Derivative [Line Items]
Average Monthly Notional	39,195	30,930
Warrants
Derivative [Line Items]
Average Monthly Notional	$ 1,541	$ 2,222