STATUTORY INFORMATION AND DIVIDEND RESTRICTIONS (Details) (USD $)	12 Months Ended				12 Months Ended				12 Months Ended
	Dec. 31, 2013 item	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2013 RLI Ins.	Dec. 31, 2012 RLI Ins.	Dec. 31, 2011 RLI Ins.	Dec. 31, 2013 Mt. Hawley Insurance Company	Dec. 31, 2013 Insurance subsidiaries	Dec. 31, 2012 Insurance subsidiaries	Dec. 31, 2011 Insurance subsidiaries	Dec. 31, 2013 Common stock security Mt. Hawley Insurance Company	Dec. 31, 2012 Common stock security Mt. Hawley Insurance Company	Dec. 31, 2011 Common stock security Mt. Hawley Insurance Company
STATUTORY INFORMATION AND DIVIDEND RESTRICTIONS
Number of insurance companies	4
Equity	$ 828,966,000	$ 796,363,000	$ 792,634,000	$ 769,151,000
Remaining unrestricted equity, liquid assets	32,000,000
Statutory information and dividend restrictions
Authorized control level RBC					90,600,000	90,400,000	89,300,000
Cost basis of RLI stock held by the subsidiary								64,600,000
Selected information for insurance subsidiaries
Consolidated net income, statutory basis									122,550,000	125,672,000	118,922,000
Consolidated surplus, statutory basis					859,200,000	684,100,000	710,200,000		859,221,000	684,072,000	710,186,000	64,000,000	9,100,000	14,700,000
Dividend restriction as percentage of policyholder surplus	10.00%
Ordinary dividends paid					40,000,000	13,000,000	0
Extraordinary dividend paid after seeking and receiving approval from the Illinois regulatory authorities					0	125,000,000	150,000,000
Non restricted net assets									$ 92,700,000