v3.25.2
Cover Page - shares
 6 Months Ended
Jun. 30, 2025
Jul. 28, 2025
Document Information [Line Items]    
Entity Central Index Key 0001587732  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q2  
Amendment Flag false  
Entity Information [Line Items]    
Document Type 10-Q  
Document Period End Date Jun. 30, 2025  
Document Transition Report false  
Entity File Number 001-36108  
Entity Registrant Name ONE Gas, Inc.  
Entity Incorporation, State or Country Code OK  
Entity Tax Identification Number 46-3561936  
Entity Address, Address Line One 15 East Fifth Street  
Entity Address, City or Town Tulsa,  
Entity Address, State or Province OK  
Entity Address, Postal Zip Code 74103  
City Area Code (918)  
Local Phone Number 947-7000  
Title of 12(b) Security Common Stock, par value $0.01 per share  
Trading Symbol OGS  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   59,998,366
Document Quarterly Report true