v3.26.1
Cover Page - shares
 3 Months Ended
Mar. 31, 2026
May 04, 2026
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2026  
Document Transition Report false  
Entity File Number 001-36777  
Entity Registrant Name JAMES RIVER GROUP HOLDINGS, INC.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 98-0585280  
Entity Address, Address Line One 1414 Raleigh Road  
Entity Address, Address Line Two Suite 405  
Entity Address, City or Town Chapel Hill  
Entity Address, State or Province NC  
Entity Address, Postal Zip Code 27517  
City Area Code 919  
Local Phone Number 900-1200  
Title of 12(b) Security Common Stock, par value $0.0002 per share  
Trading Symbol JRVR  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   46,236,856
Entity Central Index Key 0001620459  
Current Fiscal Year End Date --12-31  
Amendment Flag false  
Document Fiscal Period Focus Q1  
Document Fiscal Year Focus 2026