Investment in Loans (Schedule of Commercial Mortgage Loans) (Details) (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Mar. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance		$ 1,536,714	$ 1,417,054
Unamortized Premium (Discount)		(156,693)	(196,118)
Loans, at fair value	[1],[2]	$ 1,582,516	$ 1,453,480
Weighted Average
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Coupon		3.68%	3.92%
Weighted Average Yield		3.62%	4.77%
Weighted average life		5 years 4 months 17 days	4 years 5 months 26 days
Commercial mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance		$ 235,077	$ 212,716
Unamortized Premium (Discount)		1,110	290
Investments, at fair value, Cost		236,187	213,006
Gains		216	479
Losses		(455)	(454)
Loans, at fair value		235,948	$ 213,031
Number of mortgage loans in process of foreclosure			1
Mortgage Loans in Process of Foreclosure, Amount			$ 10,500
Commercial mortgage loans | Non-performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance		34,400	31,800
Loans, at fair value		$ 34,300	$ 31,500
Commercial mortgage loans | Weighted Average
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Coupon		8.19%	8.38%
Weighted Average Yield		8.19%	8.28%
Weighted average life		9 months 29 days	7 months 13 days
Non-accrual status [Member] | Commercial mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at fair value			$ 31,500
Non-accrual status [Member] | Commercial mortgage loans | Non-performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, at fair value		$ 34,300

[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.

[2] Includes assets pledged as collateral to counterparties. See Note 11 for additional details on the Company's borrowings and related collateral.