Cover - shares	3 Months Ended
	Mar. 31, 2021	May 10, 2021
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	001-35845
Entity Registrant Name	LUMENT FINANCE TRUST, INC.
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	45-4966519
Entity Address, Address Line One	230 Park Avenue, 23rd Floor
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10169
City Area Code	212
Local Phone Number	521-6323
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		24,943,383
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001547546
Current Fiscal Year End Date	--12-31
Common Stock
Entity Information [Line Items]
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	LFT
Security Exchange Name	NYSE
Redeemable Preferred Stock
Entity Information [Line Items]
Title of 12(b) Security	7.875% Series A Cumulative Redeemable Preferred Stock, par value $0.01 per share
Trading Symbol	LFTPrA
Security Exchange Name	NYSE