HISTORICAL LOSS AND LAE DEVELOPMENT - Unpaid Losses and Settlement Expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Unpaid losses and LAE at beginning of year:
Gross	$ 1,139,337	$ 1,103,785
Ceded	(288,224)	(297,844)
Net	851,113	805,941
Increase (decrease) in incurred losses and LAE:
Current accident year	99,249	95,161
Prior accident years	(5,859)	(13,990)
Total incurred	93,390	81,171
Loss and LAE payments for claims incurred:
Current accident year	(3,395)	(4,405)
Prior accident year	(60,427)	(58,584)
Total paid	(63,822)	(62,989)
Net unpaid losses and LAE at end of year	851,113	805,941	$ 880,681	$ 824,123
Unpaid losses and LAE at end of year:
Gross	1,152,027	1,121,363
Ceded	(271,346)	(297,240)
Net	$ 851,113	$ 805,941	$ 880,681	$ 824,123