FAIR VALUE MEASUREMENTS (DETAILS 2) $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($) degree_day	Dec. 31, 2015 USD ($)
Fair Value Inputs Assets Quantitative Information [Line Items]
Other investments	$ 830,219	$ 816,756
Discounted cash flow [Member] \| Level 3 [Member] \| Other Investments - CLO-Equities [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Other investments	$ 34,941
Default rates	4.00%
Discounted cash flow [Member] \| Level 3 [Member] \| Other Privately Held Investments [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Other investments	$ 42,142
Liquidation value [Member] \| Level 3 [Member] \| Other Investments - CLO-Equities [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Other investments	$ 25,759
Fair value of collateral	100.00%
Simulation Model [Member] \| Level 3 [Member] \| Weather Related Derivative [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Net derivative assets	$ (3,968)
Minimum [Member] \| Discounted cash flow [Member] \| Level 3 [Member] \| Other Investments - CLO-Equities [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Loss severity rate	35.00%
Collateral spreads	3.00%
Estimated maturity dates (years)	2 years
Minimum [Member] \| Discounted cash flow [Member] \| Level 3 [Member] \| Other Privately Held Investments [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Discount rate	5.00%
Minimum [Member] \| Liquidation value [Member] \| Level 3 [Member] \| Other Investments - CLO-Equities [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Discount Margin	0.40%
Minimum [Member] \| Simulation Model [Member] \| Level 3 [Member] \| Weather Related Derivative [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Weather curve \| degree_day	1
Weather standard deviation \| degree_day	1
Maximum [Member] \| Discounted cash flow [Member] \| Level 3 [Member] \| Other Investments - CLO-Equities [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Loss severity rate	53.50%
Collateral spreads	3.60%
Estimated maturity dates (years)	6 years
Maximum [Member] \| Discounted cash flow [Member] \| Level 3 [Member] \| Other Privately Held Investments [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Discount rate	8.00%
Maximum [Member] \| Liquidation value [Member] \| Level 3 [Member] \| Other Investments - CLO-Equities [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Discount Margin	16.40%
Maximum [Member] \| Simulation Model [Member] \| Level 3 [Member] \| Weather Related Derivative [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Weather curve \| degree_day	5,545
Weather standard deviation \| degree_day	1,029
Weighted Average [Member] \| Discounted cash flow [Member] \| Level 3 [Member] \| Other Investments - CLO-Equities [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Default rates	4.00%
Loss severity rate	35.40%
Collateral spreads	3.00%
Estimated maturity dates (years)	6 years
Weighted Average [Member] \| Discounted cash flow [Member] \| Level 3 [Member] \| Other Privately Held Investments [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Discount rate	7.20%
Weighted Average [Member] \| Liquidation value [Member] \| Level 3 [Member] \| Other Investments - CLO-Equities [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Fair value of collateral	100.00%
Discount Margin	2.00%

Percentage of fair value of the underlying collateral, used as an input to measure fair value.

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- Definition

The difference between the interest yield earned on the underlying collateral assets and the interest rates incurred on the debt tranches of the CLO structure.

+ References

No definition available.

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- Definition

Discount margin applied to underlying collateral, used as an input to measure fair value.

+ References

No definition available.

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- Definition

The estimated remaining time to maturity of the CLO structure (expressed as a number of years).

+ References

No definition available.

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- Definition

Fair value inputs, heating degree days.

+ References

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Fair value inputs, standard deviation of heating degree days.

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No definition available.

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- Definition

Fair value of investments in certain entities that calculate net asset value per share, including, but not limited to, by unit, membership interest, or other ownership interest. Investments include, but are not limited to, investments in certain hedge funds, venture capital funds, private equity funds, real estate partnerships or funds.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=SL6742756-110258

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- Definition

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Loss, including interest and principal, incurred on a defaulted security, expressed as a percentage of the original principal balance, used as an input to measure fair value.

+ References

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- Definition

Percentage of likelihood a loan will not be repaid and instead default, used as an input to measure fair value.

+ References

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