LIABILITY FOR LOSSES AND SETTLEMENT EXPENSES RECONCILIATION TO LIABILITY (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Short-duration insurance contracts, reconciliation of claims development to liability [Line Items]
Net outstanding liability	$ 643,448
Ceded reserves	20,664	$ 23,477	$ 28,253	$ 30,118
Unallocated settlement expenses	26,420
Gross reserve for losses and settlement expenses	690,532	$ 678,774	$ 661,309	$ 610,181
Commercial Auto Liability [Member]
Short-duration insurance contracts, reconciliation of claims development to liability [Line Items]
Net outstanding liability	100,252
Ceded reserves	526
Commercial Property [Member]
Short-duration insurance contracts, reconciliation of claims development to liability [Line Items]
Net outstanding liability	30,371
Ceded reserves	3,608
Workers' Compensation [Member]
Short-duration insurance contracts, reconciliation of claims development to liability [Line Items]
Net outstanding liability	136,782
Ceded reserves	8,265
Other Liability [Member]
Short-duration insurance contracts, reconciliation of claims development to liability [Line Items]
Net outstanding liability	163,781
Ceded reserves	2,547
Personal Auto Liability [Member]
Short-duration insurance contracts, reconciliation of claims development to liability [Line Items]
Net outstanding liability	9,000
Ceded reserves	1,511
Homeowners Insurance [Member]
Short-duration insurance contracts, reconciliation of claims development to liability [Line Items]
Net outstanding liability	2,445
Ceded reserves	41
Auto Physical Damage [Member]
Short-duration insurance contracts, reconciliation of claims development to liability [Line Items]
Net outstanding liability	998
Ceded reserves	21
Assumed Pro Rata [Member]
Short-duration insurance contracts, reconciliation of claims development to liability [Line Items]
Net outstanding liability	58,459
Ceded reserves	2,242
Assumed Excess of Loss [Member]
Short-duration insurance contracts, reconciliation of claims development to liability [Line Items]
Net outstanding liability	139,393
Ceded reserves	1,880
Other Short-duration Insurance Product Line [Member]
Short-duration insurance contracts, reconciliation of claims development to liability [Line Items]
Net outstanding liability	1,967
Ceded reserves	$ 23