(Schedule of Reverse Repurchase Agreements by Maturity) (Details) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2021 USD ($) counterparty	Dec. 31, 2020 USD ($) counterparty
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	[1]	$ 2,105,836	$ 1,496,931
Number of Counterparties with Outstanding Reverse Repurchase Agreements | counterparty		24	24
Total secured borrowings		$ 3,100,000	$ 2,300,000
Agency RMBS
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		1,436,845	921,862
Agency RMBS | 30 Days or Less
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		367,272	265,556
Agency RMBS | 31-60 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		140,143	385,141
Agency RMBS | 61-90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		20,351	174,586
Agency RMBS | 91-120 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		37,029	0
Agency RMBS | 151 to 180 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		83,344	59,857
Agency RMBS | 121-150 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		196,073	2,692
Agency RMBS | More Than 360 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		592,633	34,030
Credit
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		668,991	575,069
Credit | 30 Days or Less
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		28,508	37,795
Credit | 31-60 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		95,264	84,554
Credit | 61-90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		374,547	152,426
Credit | 91-120 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		23,758	89,931
Credit | 151 to 180 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		7,091	11,063
Credit | Total Credit Assets
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		33,934	94,248
Credit | 121-150 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		0	66,412
Credit | More Than 360 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		$ 105,889	$ 38,640
Minimum
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		0.10%	0.20%
Repurchase agreements, remaining days to maturity		1 day	4 days
Maximum
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		3.75%	5.00%
Repurchase agreements, remaining days to maturity		730 days	516 days
Weighted Average
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		0.80%	1.20%
Repurchase agreements, remaining days to maturity		147 days	94 days
Weighted Average | Agency RMBS
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		0.17%	0.27%
Repurchase agreements, remaining days to maturity		157 days	57 days
Weighted Average | Agency RMBS | 30 Days or Less
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		0.14%	0.28%
Repurchase agreements, remaining days to maturity		13 days	17 days
Weighted Average | Agency RMBS | 31-60 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		0.20%	0.25%
Repurchase agreements, remaining days to maturity		43 days	44 days
Weighted Average | Agency RMBS | 61-90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		0.33%	0.28%
Repurchase agreements, remaining days to maturity		71 days	70 days
Weighted Average | Agency RMBS | 91-120 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		0.22%	0.00%
Repurchase agreements, remaining days to maturity		105 days	0 days
Weighted Average | Agency RMBS | 151 to 180 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		0.19%	0.32%
Repurchase agreements, remaining days to maturity		162 days	162 days
Weighted Average | Agency RMBS | 121-150 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		0.21%	0.27%
Repurchase agreements, remaining days to maturity		136 days	126 days
Weighted Average | Agency RMBS | More Than 360 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		0.17%	0.32%
Repurchase agreements, remaining days to maturity		286 days	252 days
Weighted Average | Non-Agency RMBS | 121-150 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements, remaining days to maturity		0 days
Weighted Average | Credit
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		2.14%	2.69%
Repurchase agreements, remaining days to maturity		126 days	155 days
Weighted Average | Credit | 30 Days or Less
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		1.23%	2.11%
Repurchase agreements, remaining days to maturity		16 days	17 days
Weighted Average | Credit | 31-60 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		1.60%	2.23%
Repurchase agreements, remaining days to maturity		48 days	50 days
Weighted Average | Credit | 61-90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		2.02%	2.11%
Repurchase agreements, remaining days to maturity		76 days	75 days
Weighted Average | Credit | 91-120 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		2.94%	2.47%
Repurchase agreements, remaining days to maturity		100 days	106 days
Weighted Average | Credit | 151 to 180 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		3.50%	2.27%
Repurchase agreements, remaining days to maturity		164 days	165 days
Weighted Average | Credit | Total Credit Assets
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		3.16%	2.99%
Repurchase agreements, remaining days to maturity		642 days	447 days
Weighted Average | Credit | 121-150 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		0.00%	4.75%
Repurchase agreements, remaining days to maturity			125 days
Weighted Average | Credit | More Than 360 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		2.71%	2.90%
Repurchase agreements, remaining days to maturity		243 days	289 days

[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.