XML 16 R1.htm IDEA: XBRL DOCUMENT v3.25.0.1
Cover Page - USD ($)
 12 Months Ended
Dec. 31, 2024
Feb. 07, 2025
Jun. 30, 2024
Document Information [Line Items]      
Document Type 10-K    
Document Annual Report true    
Document Transition Report false    
Entity Interactive Data Current Yes    
Amendment Flag false    
Document Period End Date Dec. 31, 2024    
Document Fiscal Year Focus 2024    
Document Fiscal Period Focus FY    
Entity Registrant Name UNITIL CORPORATION    
Entity Central Index Key 0000755001    
Entity File Number 1-8858    
Entity Tax Identification Number 02-0381573    
Entity Incorporation, State or Country Code NH    
Current Fiscal Year End Date --12-31    
Entity Current Reporting Status Yes    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Address, Address Line One 6 Liberty Lane West    
Entity Address, City or Town Hampton    
Entity Address, Postal Zip Code 03842-1720    
Entity Address, State or Province NH    
City Area Code 603    
Local Phone Number 772-0775    
Trading Symbol UTL    
Security Exchange Name NYSE    
Entity Common Stock, Shares Outstanding   16,245,554  
Title of 12(b) Security Common Stock    
Entity Public Float     $ 819,534,612
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
ICFR Auditor Attestation Flag true    
Documents Incorporated by Reference Portions of the Proxy Statement relating to the 2025 Unitil Corporation Annual Meeting of Shareholders to be held on April 30, 2025 are incorporated by reference into Part III of this Report.    
Auditor Name Deloitte & Touche LLP    
Auditor Firm ID 34    
Auditor Location Boston, MA    
Auditor Opinion

We have audited the accompanying consolidated balance sheets of Unitil Corporation and subsidiaries (the "Company") as of December 31, 2024 and 2023, the related consolidated statements of earnings, changes in common stock equity, and cash flows, for each of the three years in the period ended December 31, 2024, and the related notes (collectively referred to as the "financial statements"). We also have audited the Company’s internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control — Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO).

In our opinion, the financial statements referred to above present fairly, in all material respects, the financial position of the Company as of December 31, 2024 and 2023, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2024, in conformity with accounting principles generally accepted in the United States of America. Also, in our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control — Integrated Framework (2013) issued by COSO.