DERIVATIVE INSTRUMENTS (Details 3) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 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	$ (23,711)	$ (3,564)	$ (30,819)	$ (3,217)
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	(2,347)	2,404	(4,719)	(116)
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	(3,620)	0	(3,181)	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	(16,385)	(5,876)	(13,628)	(2,776)
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	(1,697)	451	(9,629)	(24)
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	(543)	0	(301)
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	$ 338	$ 0	$ 338	$ 0