Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 24, 2021	Jun. 30, 2020
Cover Abstract
Entity Registrant Name	UNITED STATES LIME & MINERALS INC
Entity Central Index Key	0000082020
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	000-04197
Entity Incorporation, State or Country Code	TX
Entity Tax Identification Number	75-0789226
Entity Address, Address Line One	5429 LBJ Freeway, Suite 230
Entity Address, City or Town	Dallas
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75240
City Area Code	972
Local Phone Number	991-8400
Title of 12(b) Security	Common stock, $0.10 par value
Trading Symbol	USLM
Security Exchange Name	NASDAQ
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 173,512,467
ICFR Auditor Attestation Flag	true
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		5,653,336
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY