(Schedule of Reverse Repurchase Agreements by Maturity) (Details) $ in Thousands		3 Months Ended	12 Months Ended
		Mar. 31, 2021 USD ($) counterparty	Dec. 31, 2020 USD ($)
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements	[1]	$ 1,909,511	$ 1,496,931
Number of Counterparties with Outstanding Reverse Repurchase Agreements | counterparty		24
Total secured borrowings		$ 2,900,000	2,300,000
Agency RMBS
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		1,436,506	921,862
Agency RMBS | 30 Days or Less
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		223,518	265,556
Agency RMBS | 31-60 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		549,479	385,141
Agency RMBS | 61-90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		182,827	174,586
Agency RMBS | 91-120 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		7,520	0
Agency RMBS | 151 to 180 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		79,809	59,857
Agency RMBS | 121-150 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		152,660	2,692
Agency RMBS | More Than 360 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		240,693	34,030
Credit
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		473,005	575,069
Credit | 30 Days or Less
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		14,646	37,795
Credit | 31-60 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		147,187	84,554
Credit | 61-90 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		103,919	152,426
Credit | 91-120 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		78,396	89,931
Credit | 151 to 180 Days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		5,877	11,063
Credit | Total Credit Assets
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase agreements		81,095	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		$ 41,885	$ 38,640
Minimum
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		0.15%	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		5.00%	5.00%
Repurchase agreements, remaining days to maturity		672 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		118 days	94 days
Weighted Average | Agency RMBS
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Interest Rate		0.22%	0.27%
Repurchase agreements, remaining days to maturity		107 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		0.23%	0.28%
Repurchase agreements, remaining days to maturity		16 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		0.29%	0.28%
Repurchase agreements, remaining days to maturity		73 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		1.03%	0.00%
Repurchase agreements, remaining days to maturity		92 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		0.20%	0.32%
Repurchase agreements, remaining days to maturity		168 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		0.20%	0.27%
Repurchase agreements, remaining days to maturity		135 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		0.21%	0.32%
Repurchase agreements, remaining days to maturity		326 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		2.57%	2.69%
Repurchase agreements, remaining days to maturity		149 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		1.87%	2.11%
Repurchase agreements, remaining days to maturity		14 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		3.03%	2.23%
Repurchase agreements, remaining days to maturity		42 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		1.81%	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		2.22%	2.47%
Repurchase agreements, remaining days to maturity		106 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		3.75%	2.27%
Repurchase agreements, remaining days to maturity		168 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		2.85%	2.99%
Repurchase agreements, remaining days to maturity		446 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		2.98%	2.90%
Repurchase agreements, remaining days to maturity		256 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.