v3.26.3
Document and Entity Information Document - shares
 9 Months Ended
Sep. 30, 2026
Oct. 16, 2026
Document and Entity Information [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Transition Report false  
Document Period End Date Sep. 30, 2026  
Entity Registrant Name KINSALE CAPITAL GROUP, INC.  
Entity File Number 001-37848  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 98-0664337  
Entity Address, Address Line One 2025 Staples Mill Road  
Entity Address, City or Town Richmond  
Entity Address, State or Province VA  
Entity Address, Postal Zip Code 23230  
Entity Current Reporting Status Yes  
City Area Code 804  
Local Phone Number 289-1300  
Title of 12(b) Security Common Stock, par value $0.01 per share  
Trading Symbol KNSL  
Security Exchange Name NYSE  
Entity Filer Category Large Accelerated Filer  
Entity Emerging Growth Company false  
Entity Small Business false  
Entity Interactive Data Current Yes  
Entity Shell Company false  
Entity Central Index Key 0001669162  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q3  
Amendment Flag false  
Entity Common Stock, Shares Outstanding   22,509,945