Investment in Loans (Schedule of Commercial Mortgage Loans) (Details) (Details) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance		$ 1,940,279	$ 1,417,054
Unamortized Premium (Discount)		(143,084)	(196,118)
Loans, at fair value	[1],[2]	$ 1,996,529	$ 1,453,480
Weighted Average
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Coupon		3.63%	3.92%
Weighted Average Yield		3.45%	4.77%
Weighted average life		5 years 11 months 4 days	4 years 5 months 26 days
Commercial mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid Principal Balance		$ 267,388	$ 212,716
Unamortized Premium (Discount)		38	290
Investments, at fair value, Cost		267,426	213,006
Gains		338	479
Losses		(173)	(454)
Loans, at fair value		267,591	$ 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		39,800	31,800
Loans, at fair value		$ 40,000	$ 31,500
Commercial mortgage loans | Weighted Average
Accounts, Notes, Loans and Financing Receivable [Line Items]
Weighted Average Coupon		7.88%	8.38%
Weighted Average Yield		7.84%	8.28%
Weighted average life		11 months 23 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		$ 40,000

[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.