DERIVATIVE INSTRUMENTS (DETAILS) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Asset Derivative Fair Value	$ 6,467	$ 7,264
Liability Derivative Fair Value	18,629	18,329
Other Assets [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Asset Derivative Fair Value	6,467	7,264
Other Liabilities [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Liability Derivative Fair Value	18,629	18,329
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	198,406	161,678
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]
Asset Derivative Fair Value	490	3,925
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]
Liability Derivative Fair Value	837	12
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	140,000
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]
Asset Derivative 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]
Liability Derivative Fair Value	0	248
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	692,023	577,836
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]
Asset Derivative Fair Value	1,582	3,228
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]
Liability Derivative Fair Value	6,855	2,781
Underwriting Portfolio [Member] \| Weather-related contracts [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Notional Amount	51,395	58,124
Underwriting Portfolio [Member] \| Weather-related contracts [Member] \| Other Assets [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Asset Derivative Fair Value	4,395	111
Underwriting Portfolio [Member] \| Weather-related contracts [Member] \| Other Liabilities [Member] \| Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Liability Derivative Fair Value	10,937	15,288
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]
Asset Derivative 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]
Liability Derivative 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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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