REINSURANCE (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Premiums written
Net premiums written	$ 155,145	$ 150,939	$ 300,020	$ 293,215
Premiums earned
Net premiums earned	149,837	146,446	294,324	289,183
Losses and settlement expenses incurred
Net losses and settlement expenses incurred	107,228	102,820	203,513	187,929
Affiliated Entity [Member]
Premiums written
Assumed	136,726	128,283	261,526	247,129
Ceded	(97,585)	(101,132)	(198,529)	(200,543)
Premiums earned
Assumed	125,179	119,665	247,276	237,927
Ceded	(99,568)	(99,140)	(199,659)	(196,401)
Losses and settlement expenses incurred
Assumed	100,681	86,187	177,787	148,029
Ceded	(88,813)	(68,461)	(152,156)	(109,187)
Non Affiliated Entity [Member]
Premiums written
Direct	93,392	96,707	190,144	191,693
Assumed	36,886	38,779	71,310	73,995
Ceded	(14,274)	(11,698)	(24,431)	(19,059)
Premiums earned
Direct	95,376	94,715	191,274	187,551
Assumed	38,541	38,815	74,245	74,558
Ceded	(9,691)	(7,609)	(18,812)	(14,452)
Losses and settlement expenses incurred
Direct	72,811	66,942	135,572	107,996
Assumed	26,870	22,163	48,862	46,086
Ceded	$ (4,321)	$ (4,011)	$ (6,552)	$ (4,995)
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%	30.00%	30.00%
Premiums written
Net premiums written	$ 126,591	$ 120,533	$ 241,198	$ 231,800
Premiums earned
Net premiums earned	116,187	111,771	229,835	222,217
Losses and settlement expenses incurred
Net losses and settlement expenses incurred	81,508	81,466	157,028	143,564
Property and casualty insurance [Member] | Affiliated Entity [Member]
Premiums written
Assumed	136,726	128,283	261,526	247,129
Ceded	(96,373)	(99,862)	(196,104)	(198,003)
Premiums earned
Assumed	125,179	119,665	247,276	237,927
Ceded	(98,356)	(97,870)	(197,234)	(193,861)
Losses and settlement expenses incurred
Assumed	100,380	85,822	177,122	147,276
Ceded	(88,812)	(68,556)	(152,146)	(109,610)
Property and casualty insurance [Member] | Non Affiliated Entity [Member]
Premiums written
Direct	93,392	96,707	190,144	191,693
Assumed	1,290	1,252	2,209	2,209
Ceded	(8,444)	(5,847)	(16,577)	(11,228)
Premiums earned
Direct	95,376	94,715	191,274	187,551
Assumed	1,130	1,135	2,145	2,162
Ceded	(7,142)	(5,874)	(13,626)	(11,562)
Losses and settlement expenses incurred
Direct	72,811	66,942	135,572	107,996
Assumed	693	784	1,445	1,505
Ceded	(3,564)	(3,526)	(4,965)	(3,603)
Reinsurance [Member]
Premiums written
Net premiums written	28,554	30,406	58,822	61,415
Premiums earned
Net premiums earned	33,650	34,675	64,489	66,966
Losses and settlement expenses incurred
Net losses and settlement expenses incurred	25,720	21,354	46,485	44,365
Reinsurance [Member] | Affiliated Entity [Member]
Premiums written
Assumed	0	0	0	0
Ceded	(1,212)	(1,270)	(2,425)	(2,540)
Premiums earned
Assumed	0	0	0	0
Ceded	(1,212)	(1,270)	(2,425)	(2,540)
Losses and settlement expenses incurred
Assumed	301	365	665	753
Ceded	(1)	95	(10)	423
Reinsurance [Member] | Non Affiliated Entity [Member]
Premiums written
Direct	0	0	0	0
Assumed	35,596	37,527	69,101	71,786
Ceded	(5,830)	(5,851)	(7,854)	(7,831)
Premiums earned
Direct	0	0	0	0
Assumed	37,411	37,680	72,100	72,396
Ceded	(2,549)	(1,735)	(5,186)	(2,890)
Losses and settlement expenses incurred
Direct	0	0	0	0
Assumed	26,177	21,379	47,417	44,581
Ceded	$ (757)	$ (485)	$ (1,587)	$ (1,392)