RESERVES FOR LOSSES AND LOSS SETTLEMENT EXPENSES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross liability for losses and loss settlement expenses at beginning of year	$ 1,003,895	$ 969,437	$ 960,651
Ceded losses and loss settlement expenses	(54,653)	(63,757)	(75,150)
Net liability for losses and loss settlement expenses at beginning of year	949,242	905,680	885,501
Losses and loss settlement expenses incurred for claims occurring during
Current year	683,662	560,482	566,555
Prior years	(31,229)	(40,395)	(56,744)
Total incurred	652,433	520,087	509,811
Losses and loss settlement expense payments for claims occurring during
Current year	277,053	225,022	247,651
Prior years	260,520	251,503	241,981
Total paid	537,573	476,525	489,632
Net liability for losses and loss settlement expenses at end of year	1,064,102	949,242	905,680
Ceded loss and loss settlement expenses	59,794	54,653	63,757
Gross liability for losses and loss settlement expenses at end of year	$ 1,123,896	$ 1,003,895	$ 969,437