LOSS AND LOSS ADJUSTMENT EXPENSE RESERVES Liabilities for loss reserves (Details)	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Liability for Claims and Claims Adjustment Expense [Line Items]
Number of Operating Segments	1
Case reserves	$ 178,088,000	$ 98,815,000
IBNR	286,292,000	207,826,000
Total	464,380,000	306,641,000	$ 305,997,000	$ 264,243,000
Less: Losses recoverable	(29,459,000)	(2,704,000)	(3,368,000)	(11,523,000)
Net balance at December 31	434,921,000	303,937,000	302,629,000	252,720,000
Current Year Claims and Claims Adjustment Expense	466,247,000	345,303,000	266,796,000
Prior Year Claims and Claims Adjustment Expense	36,157,000	35,512,000	50,301,000
Incurred losses related to Total incurred	502,404,000	380,815,000	317,097,000
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	(220,298,000)	(156,181,000)	(132,017,000)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	(154,183,000)	(216,489,000)	(132,846,000)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	374,481,000	372,670,000	264,863,000
Foreign currency revaluation	(3,061,000)	6,837,000	2,325,000
Accident & Health
Liability for Claims and Claims Adjustment Expense [Line Items]
Total	22,181,000	18,993,000	21,533,000	14,137,000
Less: Losses recoverable	0	0	0	0
Net balance at December 31	22,181,000	18,993,000	21,533,000	$ 14,137,000
Current Year Claims and Claims Adjustment Expense	44,539,000	38,726,000	34,136,000
Prior Year Claims and Claims Adjustment Expense	3,739,000	(1,477,000)	(2,680,000)
Incurred losses related to Total incurred	48,278,000	37,249,000	31,456,000
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	(23,814,000)	(22,039,000)	(14,090,000)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	(21,276,000)	(17,750,000)	(9,970,000)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	45,090,000	39,789,000	24,060,000
Foreign currency revaluation	$ 0	$ 0	$ 0