HISTORICAL LOSS AND LAE DEVELOPMENT - Unpaid Losses and Settlement Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Unpaid losses and LAE at beginning of year:
Gross	$ 1,103,785	$ 1,121,040	$ 1,129,433
Ceded	(297,844)	(335,106)	(354,924)
Net	805,941	785,934	774,509
Increase (decrease) in incurred losses and LAE:
Current accident year	391,772	364,472	361,451
Prior accident years	(41,994)	(65,427)	(64,842)
Total incurred	349,778	299,045	296,609
Loss and LAE payments for claims incurred:
Current accident year	(70,540)	(71,853)	(65,308)
Prior accident year	(234,066)	(207,185)	(219,876)
Total paid	(304,606)	(279,038)	(285,184)
Net unpaid losses and LAE at end of year	805,941	785,934	774,509
Unpaid losses and LAE at end of year:
Gross	1,139,337	1,103,785	1,121,040
Ceded	(288,224)	(297,844)	(335,106)
Net	$ 851,113	$ 805,941	$ 785,934