SEGMENT INFORMATION - Summarized financial information by segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Reconciliation of operating profit loss from segment to consolidated
Premiums earned	$ 155,786	$ 144,487
SAP underwriting profit (loss)	(7,473)	653
GAAP adjustments	364	(2,618)
GAAP underwriting profit (loss)	(7,109)	(1,965)
Net investment income	11,371	11,007
Net realized investment gains (losses) and, beginning in 2018, change in unrealized investment gains on equity investments	(5,393)	(627)
Other income (loss)	1,615	870
Interest expense	142	84
Other expenses	870	761
Income (loss) before income tax expense (benefit)	(528)	8,440
Reconciliation of assets from segment to consolidated
Assets	2,248,068		$ 2,289,419
Eliminations	(576,656)		(599,036)
Reclassifications	(6,259)		(8,443)
Total assets	1,665,153		1,681,940
Property and casualty insurance [Member]
Reconciliation of operating profit loss from segment to consolidated
Premiums earned	118,632	113,648
SAP underwriting profit (loss)	(9,036)	(2,594)
GAAP adjustments	262	(2,287)
GAAP underwriting profit (loss)	(8,774)	(4,881)
Net investment income	8,148	8,015
Net realized investment gains (losses) and, beginning in 2018, change in unrealized investment gains on equity investments	(3,293)	(597)
Other income (loss)	2,051	1,441
Interest expense	142	84
Other expenses	233	179
Income (loss) before income tax expense (benefit)	(2,243)	3,715
Reconciliation of assets from segment to consolidated
Assets	1,185,069		1,200,636
Eliminations	0		0
Reclassifications	(316)		(1,393)
Total assets	1,184,753		1,199,243
Reinsurance [Member]
Reconciliation of operating profit loss from segment to consolidated
Premiums earned	37,154	30,839
SAP underwriting profit (loss)	1,563	3,247
GAAP adjustments	102	(331)
GAAP underwriting profit (loss)	1,665	2,916
Net investment income	3,218	2,983
Net realized investment gains (losses) and, beginning in 2018, change in unrealized investment gains on equity investments	(2,100)	(30)
Other income (loss)	(436)	(571)
Interest expense	0	0
Other expenses	0	0
Income (loss) before income tax expense (benefit)	2,347	5,298
Reconciliation of assets from segment to consolidated
Assets	481,257		484,678
Eliminations	0		0
Reclassifications	(5,045)		(6,273)
Total assets	476,212		478,405
Parent company [Member]
Reconciliation of operating profit loss from segment to consolidated
Premiums earned	0	0
SAP underwriting profit (loss)	0	0
GAAP adjustments	0	0
GAAP underwriting profit (loss)	0	0
Net investment income	5	9
Net realized investment gains (losses) and, beginning in 2018, change in unrealized investment gains on equity investments	0	0
Other income (loss)	0	0
Interest expense	0	0
Other expenses	637	582
Income (loss) before income tax expense (benefit)	(632)	$ (573)
Reconciliation of assets from segment to consolidated
Assets	581,742		604,105
Eliminations	(576,656)		(599,036)
Reclassifications	(898)		(777)
Total assets	$ 4,188		$ 4,292