Investment in Securities (Maturities of Securities) (Details) - USD ($) $ in Thousands		Sep. 30, 2020	Dec. 31, 2019
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)	[1]	$ 1,451,420	$ 2,449,941
Amortized Cost		$ 1,430,336	$ 2,342,369
Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.98%	4.23%
Long
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 1,451,420	$ 2,449,941
Amortized Cost		$ 1,479,723	$ 2,415,210
Long | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.86%	4.15%
Long | Agency RMBS
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 868,150	$ 1,901,684
Amortized Cost		$ 835,904	$ 1,886,235
Long | Agency RMBS | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.99%	4.02%
Long | Agency RMBS | Less than three years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 150,492	$ 188,593
Amortized Cost		$ 146,624	$ 187,099
Long | Agency RMBS | Less than three years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		4.26%	3.39%
Long | Agency RMBS | Greater than three years less than seven years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 706,422	$ 961,839
Amortized Cost		$ 678,227	$ 953,031
Long | Agency RMBS | Greater than three years less than seven years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.95%	4.25%
Long | Agency RMBS | Greater than seven years less than eleven [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 11,236	$ 713,862
Amortized Cost		$ 11,053	$ 708,805
Long | Agency RMBS | Greater than seven years less than eleven [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.01%	3.89%
Long | Agency RMBS | Greater than eleven year [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 0	$ 37,390
Amortized Cost		$ 0	$ 37,300
Long | Agency RMBS | Greater than eleven year [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		0.00%	3.51%
Long | Agency RMBS | Interest only securities
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 51,705	$ 35,279
Amortized Cost		$ 47,507	$ 34,044
Long | Agency RMBS | Interest only securities | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.47%	2.81%
Long | Agency RMBS | Interest only securities | Less than three years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 8,893	$ 9,011
Amortized Cost		$ 8,267	$ 8,611
Long | Agency RMBS | Interest only securities | Less than three years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.90%	3.35%
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)		$ 39,604	$ 25,334
Amortized Cost		$ 36,038	$ 24,512
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%	2.66%
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)		$ 1,048	$ 934
Amortized Cost		$ 1,049	$ 921
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		0.28%	1.90%
Long | Agency RMBS | Interest only securities | Greater than eleven year [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 2,160	$ 0
Amortized Cost		$ 2,153	$ 0
Long | Agency RMBS | Interest only securities | Greater than eleven year [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		0.78%	0.00%
Long | Non-Agency RMBS and CMBS
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 307,803	$ 283,102
Amortized Cost		$ 326,778	$ 269,124
Long | Non-Agency RMBS and CMBS | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		2.93%	3.37%
Long | Non-Agency RMBS and CMBS | Less than three years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 80,873	$ 50,120
Amortized Cost		$ 77,739	$ 48,213
Long | Non-Agency RMBS and CMBS | Less than three years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.67%	2.73%
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)		$ 106,561	$ 87,436
Amortized Cost		$ 102,374	$ 79,326
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		3.38%	4.42%
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)		$ 96,327	$ 127,533
Amortized Cost		$ 119,267	$ 123,924
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		2.48%	3.31%
Long | Non-Agency RMBS and CMBS | Greater than eleven year [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 24,042	$ 18,013
Amortized Cost		$ 27,398	$ 17,661
Long | Non-Agency RMBS and CMBS | Greater than eleven year [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		1.04%	0.81%
Long | Non-Agency RMBS
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 209,550	$ 163,136
Amortized Cost		$ 205,021	$ 151,668
Long | Non-Agency RMBS | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		3.16%	3.41%
Long | Non-Agency RMBS | Interest only securities
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 9,949	$ 8,316
Amortized Cost		$ 8,367	$ 6,517
Long | Non-Agency RMBS | Interest only securities | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		1.17%	1.10%
Long | Non-Agency RMBS | Interest only securities | Less than three years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 4,079	$ 439
Amortized Cost		$ 2,685	$ 401
Long | Non-Agency RMBS | Interest only securities | Less than three years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		0.55%	1.37%
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)		$ 5,870	$ 7,877
Amortized Cost		$ 5,682	$ 6,116
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		1.47%	1.08%
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)		$ 0	$ 0
Amortized Cost		$ 0	$ 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		0.00%	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)		$ 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)		$ 212,799	$ 220,166
Amortized Cost		$ 259,563	$ 218,048
Long | CLOs And Other Securities [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		4.84%	6.60%
Long | CLOs And Other Securities [Member] | Less than three years [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 61,222	$ 54,446
Amortized Cost		$ 63,694	$ 54,090
Long | CLOs And Other Securities [Member] | Less than three years [Member] | Weighted Average
Securities, Available-for-sale [Line Items]
Weighted Average Coupon		9.43%	11.11%
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)		$ 150,175	$ 157,384
Amortized Cost		$ 193,955	$ 155,651
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		3.38%	5.38%
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)		$ 1,402	$ 8,336
Amortized Cost		$ 1,914	$ 8,307
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%	0.00%
Long | CLOs And Other Securities [Member] | Greater than eleven year [Member]
Securities, Available-for-sale [Line Items]
Securities, at fair value(1)		$ 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.