Document and Entity Information
Jan. 31, 2023
Document and Entity Information [Abstract]  
Document Type 8-K
Document Period End Date Jan. 31, 2023
Entity Registrant Name RLI Corp.
Entity Incorporation, State or Country Code DE
Entity File Number 001-09463
Entity Tax Identification Number 37-0889946
Entity Address, Address Line One 9025 North Lindbergh Drive
Entity Address, City or Town Peoria
Entity Address State Or Province IL
Entity Address, Postal Zip Code 61615
City Area Code 309
Local Phone Number 692-1000
Written Communications false
Soliciting Material false
Pre-commencement Tender Offer false
Pre-commencement Issuer Tender Offer false
Title of 12(b) Security Common Stock $0.01 par value
Trading Symbol RLI
Security Exchange Name NYSE
Entity Emerging Growth Company false
Entity Central Index Key 0000084246
Amendment Flag false