Investment in Securities (Maturities of Securities) (Details) - USD ($) $ in Thousands		Sep. 30, 2021	Dec. 31, 2020
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)	[1],[2]	$ 1,895,563	$ 1,514,185
Amortized Cost		$ 1,856,210	$ 1,474,155
Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.63%	3.92%
Long
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 1,895,563	$ 1,514,185
Amortized Cost		$ 1,885,646	$ 1,508,997
Long | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.57%	3.84%
Long | Agency RMBS
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 1,498,930	$ 911,787
Amortized Cost		$ 1,490,830	$ 881,270
Long | Agency RMBS | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.10%	3.84%
Long | Agency RMBS | Less than three years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 48,284	$ 139,059
Amortized Cost		$ 47,527	$ 135,844
Long | Agency RMBS | Less than three years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		4.05%	4.15%
Long | Agency RMBS | Greater than three years less than seven years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 977,274	$ 770,173
Amortized Cost		$ 970,123	$ 742,946
Long | Agency RMBS | Greater than three years less than seven years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.31%	3.79%
Long | Agency RMBS | Greater than seven years less than eleven [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 472,327	$ 2,555
Amortized Cost		$ 472,137	$ 2,480
Long | Agency RMBS | Greater than seven years less than eleven [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		2.56%	3.01%
Long | Agency RMBS | Greater than eleven year [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 1,045	$ 0
Amortized Cost		$ 1,043	$ 0
Long | Agency RMBS | Greater than eleven year [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		2.00%	0.00%
Long | Agency RMBS | Interest only securities
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 38,077	$ 47,656
Amortized Cost		$ 35,948	$ 43,406
Long | Agency RMBS | Interest only securities | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.51%	3.36%
Long | Agency RMBS | Interest only securities | Less than three years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 7,496	$ 8,143
Amortized Cost		$ 7,032	$ 7,314
Long | Agency RMBS | Interest only securities | Less than three years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.54%	3.99%
Long | Agency RMBS | Interest only securities | Greater than three years less than seven years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 28,763	$ 32,669
Amortized Cost		$ 27,162	$ 29,362
Long | Agency RMBS | Interest only securities | Greater than three years less than seven years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.63%	3.74%
Long | Agency RMBS | Interest only securities | Greater than seven years less than eleven [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 1,818	$ 5,165
Amortized Cost		$ 1,754	$ 5,063
Long | Agency RMBS | Interest only securities | Greater than seven years less than eleven [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		1.43%	1.04%
Long | Agency RMBS | Interest only securities | Greater than eleven year [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 0	$ 1,679
Amortized Cost		$ 0	$ 1,667
Long | Agency RMBS | Interest only securities | Greater than eleven year [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		0.00%	0.83%
Long | Non-Agency RMBS and CMBS
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 195,808	$ 312,157
Amortized Cost		$ 191,028	$ 317,081
Long | Non-Agency RMBS and CMBS | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		4.53%	2.98%
Long | Non-Agency RMBS and CMBS | Less than three years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 73,102	$ 58,350
Amortized Cost		$ 68,824	$ 54,339
Long | Non-Agency RMBS and CMBS | Less than three years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		5.06%	3.39%
Long | Non-Agency RMBS and CMBS | Greater than three years less than seven years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 56,905	$ 114,815
Amortized Cost		$ 54,286	$ 109,161
Long | Non-Agency RMBS and CMBS | Greater than three years less than seven years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.57%	3.45%
Long | Non-Agency RMBS and CMBS | Greater than seven years less than eleven [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 54,517	$ 109,519
Amortized Cost		$ 56,473	$ 123,782
Long | Non-Agency RMBS and CMBS | Greater than seven years less than eleven [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		5.33%	2.74%
Long | Non-Agency RMBS and CMBS | Greater than eleven year [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 11,284	$ 29,473
Amortized Cost		$ 11,445	$ 29,799
Long | Non-Agency RMBS and CMBS | Greater than eleven year [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		1.93%	1.46%
Long | Non-Agency RMBS
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 185,010	$ 201,090
Amortized Cost		$ 179,586	$ 190,759
Long | Non-Agency RMBS | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		4.63%	3.15%
Long | Non-Agency RMBS | Interest only securities
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 11,349	$ 9,610
Amortized Cost		$ 9,999	$ 8,123
Long | Non-Agency RMBS | Interest only securities | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		0.98%	1.17%
Long | Non-Agency RMBS | Interest only securities | Less than three years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 2,172	$ 5,163
Amortized Cost		$ 1,324	$ 3,754
Long | Non-Agency RMBS | Interest only securities | Less than three years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		0.00%	0.92%
Long | Non-Agency RMBS | Interest only securities | Greater than three years less than seven years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 4,142	$ 4,447
Amortized Cost		$ 3,980	$ 4,369
Long | Non-Agency RMBS | Interest only securities | Greater than three years less than seven years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		2.18%	1.37%
Long | Non-Agency RMBS | Interest only securities | Greater than seven years less than eleven [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 5,035	$ 0
Amortized Cost		$ 4,695	$ 0
Long | Non-Agency RMBS | Interest only securities | Greater than seven years less than eleven [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		0.23%	0.00%
Long | Non-Agency RMBS | Interest only securities | Greater than eleven year [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 0	$ 0
Amortized Cost		$ 0	$ 0
Long | Non-Agency RMBS | Interest only securities | Greater than eleven year [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		0.00%	0.00%
Long | CLOs And Other Securities [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 143,405	$ 231,385
Amortized Cost		$ 152,371	$ 257,513
Long | CLOs And Other Securities [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		7.36%	5.09%
Long | CLOs And Other Securities [Member] | Less than three years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 108,880	$ 89,235
Amortized Cost		$ 112,891	$ 90,869
Long | CLOs And Other Securities [Member] | Less than three years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		8.73%	7.73%
Long | CLOs And Other Securities [Member] | Greater than three years less than seven years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 34,525	$ 139,830
Amortized Cost		$ 39,480	$ 163,670
Long | CLOs And Other Securities [Member] | Greater than three years less than seven years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.43%	3.69%
Long | CLOs And Other Securities [Member] | Greater than seven years less than eleven [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 0	$ 2,320
Amortized Cost		$ 0	$ 2,974
Long | CLOs And Other Securities [Member] | Greater than seven years less than eleven [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		0.00%	1.14%
Long | CLOs And Other Securities [Member] | Greater than eleven year [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)(2)		$ 0	$ 0
Amortized Cost		$ 0	$ 0
Long | CLOs And Other Securities [Member] | Greater than eleven year [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		0.00%	0.00%

[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.