Investment in Securities (Summary of Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Securities, Available-for-sale [Line Items]
Interest Income	$ 40,079	$ 52,108
Agency RMBS
Securities, Available-for-sale [Line Items]
Coupon Interest	14,352	20,912
Net Amortization	(7,600)	(8,844)
Interest Income	6,752	12,068
Non-Agency RMBS and CMBS
Securities, Available-for-sale [Line Items]
Coupon Interest	3,756	4,053
Net Amortization	1,467	713
Interest Income	5,223	4,766
CLOs
Securities, Available-for-sale [Line Items]
Coupon Interest	2,536	5,419
Net Amortization	944	(1,011)
Interest Income	3,480	4,408
Other Securities
Securities, Available-for-sale [Line Items]
Coupon Interest	3,533	2,925
Net Amortization	(657)	(1,045)
Interest Income	2,876	1,880
Securities Investment [Member]
Securities, Available-for-sale [Line Items]
Coupon Interest	24,177	33,309
Net Amortization	(5,846)	(10,187)
Interest Income	$ 18,331	$ 23,122

The sum of the periodic adjustments of the differences between securities' face values and purchase prices that are charged against earnings. This is called accretion if the security was purchased at a discount and amortization if it was purchased at premium. As a noncash item, this element is an adjustment to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

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Amount of operating interest income, including, but not limited to, amortization and accretion of premiums and discounts on securities.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.7(b))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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