SCHEDULE IV-REINSURANCE (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
RLI Insurance Group Premiums earned
Direct amount	$ 741,569	$ 679,124	$ 625,963
Ceded to other companies	189,658	180,150	154,495
Assumed from other companies	78,891	77,597	66,984
Net amount	630,802	576,571	538,452
Percentage of amount assumed to net	12.50%	13.50%	12.40%
Casualty
RLI Insurance Group Premiums earned
Direct amount	425,105	362,724	327,411
Ceded to other companies	103,696	96,039	91,991
Assumed from other companies	2,613	1,012	778
Net amount	324,022	267,697	236,198
Percentage of amount assumed to net	0.80%	0.40%	0.30%
Property
RLI Insurance Group Premiums earned
Direct amount	203,424	203,072	194,946
Ceded to other companies	79,320	76,817	56,356
Assumed from other companies	76,037	76,147	65,070
Net amount	200,141	202,402	203,660
Percentage of amount assumed to net	38.00%	37.60%	32.00%
Surety
RLI Insurance Group Premiums earned
Direct amount	113,040	113,328	103,606
Ceded to other companies	6,642	7,294	6,148
Assumed from other companies	241	438	1,136
Net amount	$ 106,639	$ 106,472	$ 98,594
Percentage of amount assumed to net	0.20%	0.40%	1.20%