Investment in Securities (Summary of Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Securities, Available-for-sale [Line Items]
Interest Income	$ 45,890	$ 39,281	$ 85,970	$ 91,389
Agency RMBS
Securities, Available-for-sale [Line Items]
Coupon Interest	14,300	12,603	28,652	33,515
Net Amortization	(2,972)	(9,218)	(10,572)	(18,062)
Interest Income	11,328	3,385	18,080	15,453
Non-Agency RMBS and CMBS
Securities, Available-for-sale [Line Items]
Coupon Interest	3,259	3,631	7,015	7,684
Net Amortization	964	1,377	2,431	2,090
Interest Income	4,223	5,008	9,446	9,774
CLOs
Securities, Available-for-sale [Line Items]
Coupon Interest	1,909	3,987	4,445	9,406
Net Amortization	571	376	1,515	(635)
Interest Income	2,480	4,363	5,960	8,771
Other Securities
Securities, Available-for-sale [Line Items]
Coupon Interest	4,173	3,098	7,706	6,023
Net Amortization	(1,326)	(1,104)	(1,983)	(2,149)
Interest Income	2,847	1,994	5,723	3,874
Securities Investment [Member]
Securities, Available-for-sale [Line Items]
Coupon Interest	23,641	23,319	47,818	56,628
Net Amortization	(2,763)	(8,569)	(8,609)	(18,756)
Interest Income	$ 20,878	$ 14,750	$ 39,209	$ 37,872