REINSURANCE (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Premiums written
Net premiums written	$ 170,965	$ 158,072
Premiums earned
Net premiums earned	167,302	155,786
Losses and settlement expenses incurred
Net losses and settlement expenses incurred	104,969	110,628
Affiliated Entity [Member]
Premiums written
Assumed	134,343	130,201
Ceded	(109,526)	(104,337)
Premiums earned
Assumed	134,354	129,148
Ceded	(105,560)	(100,038)
Losses and settlement expenses incurred
Assumed	78,033	86,325
Ceded	(63,195)	(52,001)
Non Affiliated Entity [Member]
Premiums written
Direct	105,233	100,044
Assumed	49,700	42,139
Ceded	(8,785)	(9,975)
Premiums earned
Direct	101,267	95,745
Assumed	47,286	42,094
Ceded	(10,045)	(11,163)
Losses and settlement expenses incurred
Direct	60,935	52,287
Assumed	32,036	27,407
Ceded	$ (2,840)	$ (3,390)
Property and casualty insurance [Member]
Reinsurance Transactions For Insurance Companies, by Product Segment [Line Items]
Percentage of pool participation (in hundredths)	30.00%	30.00%
Premiums written
Net premiums written	$ 125,516	$ 120,269
Premiums earned
Net premiums earned	124,772	118,632
Losses and settlement expenses incurred
Net losses and settlement expenses incurred	76,980	83,501
Property and casualty insurance [Member] | Affiliated Entity [Member]
Premiums written
Assumed	134,343	130,201
Ceded	(108,213)	(103,024)
Premiums earned
Assumed	134,354	129,148
Ceded	(104,247)	(98,725)
Losses and settlement expenses incurred
Assumed	77,778	85,967
Ceded	(61,462)	(52,754)
Property and casualty insurance [Member] | Non Affiliated Entity [Member]
Premiums written
Direct	105,233	100,044
Assumed	965	1,018
Ceded	(6,812)	(7,970)
Premiums earned
Direct	101,267	95,745
Assumed	1,038	1,002
Ceded	(7,640)	(8,538)
Losses and settlement expenses incurred
Direct	60,935	52,287
Assumed	987	992
Ceded	(1,258)	(2,991)
Reinsurance [Member]
Premiums written
Net premiums written	45,449	37,803
Premiums earned
Net premiums earned	42,530	37,154
Losses and settlement expenses incurred
Net losses and settlement expenses incurred	27,989	27,127
Reinsurance [Member] | Affiliated Entity [Member]
Premiums written
Assumed	0	0
Ceded	(1,313)	(1,313)
Premiums earned
Assumed	0	0
Ceded	(1,313)	(1,313)
Losses and settlement expenses incurred
Assumed	255	358
Ceded	(1,733)	753
Reinsurance [Member] | Non Affiliated Entity [Member]
Premiums written
Direct	0	0
Assumed	48,735	41,121
Ceded	(1,973)	(2,005)
Premiums earned
Direct	0	0
Assumed	46,248	41,092
Ceded	(2,405)	(2,625)
Losses and settlement expenses incurred
Direct	0	0
Assumed	31,049	26,415
Ceded	$ (1,582)	$ (399)