DERIVATIVE INSTRUMENTS (Details 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Unrealized and Realized Gains (Losses) Recognized in Earnings for Derivatives Not Designated As Hedges [Line Items]
Unrealized and realized gains (losses) recognized in earnings for derivatives not designated as hedges	$ (13,262)	$ 2,605	$ (44,081)	$ (611)
Investment Portfolio [Member] | Foreign Exchange Forward Contracts [Member] | Net Realized Investment Gains (Losses) [Member]
Unrealized and Realized Gains (Losses) Recognized in Earnings for Derivatives Not Designated As Hedges [Line Items]
Unrealized and realized gains (losses) recognized in earnings for derivatives not designated as hedges	(1,815)	155	(6,534)	39
Investment Portfolio [Member] | Interest Rate Swap [Member] | Net Realized Investment Gains (Losses) [Member]
Unrealized and Realized Gains (Losses) Recognized in Earnings for Derivatives Not Designated As Hedges [Line Items]
Unrealized and realized gains (losses) recognized in earnings for derivatives not designated as hedges	520	0	(2,661)	0
Underwriting Portfolio [Member] | Foreign Exchange Forward Contracts [Member] | Foreign Exchange Gains (Losses) [Member]
Unrealized and Realized Gains (Losses) Recognized in Earnings for Derivatives Not Designated As Hedges [Line Items]
Unrealized and realized gains (losses) recognized in earnings for derivatives not designated as hedges	(12,481)	(182)	(26,109)	(2,958)
Underwriting Portfolio [Member] | Weather Related Derivative [Member] | Other Insurance Related Income [Member]
Unrealized and Realized Gains (Losses) Recognized in Earnings for Derivatives Not Designated As Hedges [Line Items]
Unrealized and realized gains (losses) recognized in earnings for derivatives not designated as hedges	0	833	(9,629)	809
Underwriting Portfolio [Member] | Commodity Contract [Member] | Other Insurance Related Income [Member]
Unrealized and Realized Gains (Losses) Recognized in Earnings for Derivatives Not Designated As Hedges [Line Items]
Unrealized and realized gains (losses) recognized in earnings for derivatives not designated as hedges	0	1,799	0	1,499
Other Underwriting-related Contracts [Member] | Commodity Contract [Member] | Other Insurance Related Income [Member]
Unrealized and Realized Gains (Losses) Recognized in Earnings for Derivatives Not Designated As Hedges [Line Items]
Unrealized and realized gains (losses) recognized in earnings for derivatives not designated as hedges	$ 514	$ 0	$ 852	$ 0