DERIVATIVE INSTRUMENTS (DETAILS) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Asset Fair Value	$ 16,897	$ 6,467
Derivative Liability Fair Value	15,576	18,629
Other Assets [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Asset Fair Value	16,897	6,467
Other Liabilities [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Liability Fair Value	15,576	18,629
Investment Portfolio [Member] \| Foreign Exchange Forward Contracts [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Notional Amount	195,979	198,406
Investment Portfolio [Member] \| Foreign Exchange Forward Contracts [Member] \| Other Assets [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Asset Fair Value	12,331	490
Investment Portfolio [Member] \| Foreign Exchange Forward Contracts [Member] \| Other Liabilities [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Liability Fair Value	87	837
Investment Portfolio [Member] \| Interest Rate Swap [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Notional Amount	0	0
Investment Portfolio [Member] \| Interest Rate Swap [Member] \| Other Assets [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Asset Fair Value	0	0
Investment Portfolio [Member] \| Interest Rate Swap [Member] \| Other Liabilities [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Liability Fair Value	0	0
Underwriting Portfolio [Member] \| Foreign Exchange Forward Contracts [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Notional Amount	492,899	692,023
Underwriting Portfolio [Member] \| Foreign Exchange Forward Contracts [Member] \| Other Assets [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Asset Fair Value	2,034	1,582
Underwriting Portfolio [Member] \| Foreign Exchange Forward Contracts [Member] \| Other Liabilities [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Liability Fair Value	8,989	6,855
Underwriting Portfolio [Member] \| Weather Related Derivative [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Notional Amount	67,957	51,395
Underwriting Portfolio [Member] \| Weather Related Derivative [Member] \| Other Assets [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Asset Fair Value	2,532	4,395
Underwriting Portfolio [Member] \| Weather Related Derivative [Member] \| Other Liabilities [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Liability Fair Value	6,500	10,937
Underwriting Portfolio [Member] \| Commodity Contract [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Notional Amount	0	0
Underwriting Portfolio [Member] \| Commodity Contract [Member] \| Other Assets [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Asset Fair Value	0	0
Underwriting Portfolio [Member] \| Commodity Contract [Member] \| Other Liabilities [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Liability Fair Value	$ 0	$ 0

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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