Investment in Loans (Schedule of Commercial Mortgage Loans) (Details) (Details) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance		$ 1,414,410	$ 1,387,733
Unamortized Premium (Discount)		(202,583)	(150,821)
Loans, at fair value	[1]	$ 1,442,612	$ 1,412,426
Weighted Average
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Coupon		3.98%	4.23%
Weighted Average Yield		4.89%	4.01%
Weighted average life		4 years 4 months 17 days	5 years 10 months 24 days
Commercial mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance		$ 252,305	$ 277,870
Unamortized Premium (Discount)		(122)	(3,302)
Amortized Cost		252,183	274,568
Gains		535	253
Losses		(487)	(62)
Loans, at fair value		$ 252,231	$ 274,759
Number of mortgage loans in process of foreclosure			2
Mortgage Loans in Process of Foreclosure, Amount			$ 16,000
Commercial mortgage loans | Weighted Average
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Coupon		8.25%	7.65%
Weighted Average Yield		8.14%	8.58%
Weighted average life		9 months 7 days	1 year 25 days
Non-accrual status [Member] | Commercial mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at fair value		$ 23,800	$ 10,700

[1] Ellington Financial Inc.'s Condensed Consolidated Balance Sheet includes assets and liabilities of variable interest entities it has consolidated. See Note 9 for additional details on Ellington Financial Inc.'s consolidated variable interest entities.