XML 23 R1.htm IDEA: XBRL DOCUMENT v3.25.0.1
Document And Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2024
Mar. 07, 2025
Jun. 30, 2024
Document Information [Line Items]      
Entity Central Index Key 0000903419    
Entity Registrant Name ALERUS FINANCIAL CORP    
Amendment Flag false    
Current Fiscal Year End Date --12-31    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2024    
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2024    
Document Transition Report false    
Entity File Number 001-39036    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 45-0375407    
Entity Address, Address Line One 401 Demers Avenue    
Entity Address, City or Town Grand Forks    
Entity Address, State or Province ND    
Entity Address, Postal Zip Code 58201    
City Area Code 701    
Local Phone Number 795-3200    
Title of 12(b) Security Common Stock, par value $1.00 per share    
Trading Symbol ALRS    
Security Exchange Name NASDAQ    
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 Small Business false    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 368,774,658
Entity Common Stock, Shares Outstanding   25,362,855  
Auditor Name RSM US LLP    
Auditor Location Des Moines, Iowa    
Auditor Firm ID 49