SEGMENT INFORMATION - Summarized financial information by segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Reconciliation of operating profit loss from segment to consolidated
Premiums earned	$ 142,737	$ 138,731
Underwriting profit	10,476	17,084
Net investment income (loss)	12,230	11,206
Net realized investment gains (losses)	(1,085)	783
Other income (loss)	(11)	1,615
Interest expense	84	84
Other expenses	649	667
Income before income tax expense	20,877	29,937
Reconciliation of assets from segment to consolidated
Assets	2,101,943		$ 2,055,437
Eliminations	(540,576)		(514,309)
Reclassifications	(1,123)		(5,173)
Total assets	1,560,244		1,535,955
Property and casualty insurance [Member]
Reconciliation of operating profit loss from segment to consolidated
Premiums earned	110,446	108,205
Underwriting profit	8,605	14,078
Net investment income (loss)	8,771	8,026
Net realized investment gains (losses)	(846)	700
Other income (loss)	132	182
Interest expense	84	84
Other expenses	157	206
Income before income tax expense	16,421	22,696
Reconciliation of assets from segment to consolidated
Assets	1,097,040		1,092,820
Eliminations	0		0
Reclassifications	0		0
Total assets	1,097,040		1,092,820
Reinsurance [Member]
Reconciliation of operating profit loss from segment to consolidated
Premiums earned	32,291	30,526
Underwriting profit	1,871	3,006
Net investment income (loss)	3,457	3,184
Net realized investment gains (losses)	(239)	83
Other income (loss)	(143)	1,433
Interest expense	0	0
Other expenses	0	0
Income before income tax expense	4,946	7,706
Reconciliation of assets from segment to consolidated
Assets	453,484		437,575
Eliminations	0		0
Reclassifications	0		(5,173)
Total assets	453,484		432,402
Parent company [Member]
Reconciliation of operating profit loss from segment to consolidated
Premiums earned	0	0
Underwriting profit	0	0
Net investment income (loss)	2	(4)
Net realized investment gains (losses)	0	0
Other income (loss)	0	0
Interest expense	0	0
Other expenses	492	461
Income before income tax expense	(490)	$ (465)
Reconciliation of assets from segment to consolidated
Assets	551,419		525,042
Eliminations	(540,576)		(514,309)
Reclassifications	(1,123)		0
Total assets	$ 9,720		$ 10,733