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Fair Value Measurement (Investments in LLCs and Limited Partnerships) (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments in LPs/LLCs fair value	$ 201,154,000	$ 204,719,000
Private debt fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments LPs/LLCs unfunded commitments	11,247,000
Investments in LPs/LLCs fair value	44,520,000	55,637,000
Long equity fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments LPs/LLCs unfunded commitments	0
Investments in LPs/LLCs fair value	7,459,000	6,268,000
Long/Short equity funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments LPs/LLCs unfunded commitments	0
Investments in LPs/LLCs fair value	30,404,000	28,926,000
Non-public equity funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments LPs/LLCs unfunded commitments	85,121,000
Investments in LPs/LLCs fair value	91,707,000	89,691,000
Multi-strategy fund of funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments LPs/LLCs unfunded commitments	0
Investments in LPs/LLCs fair value	8,783,000	8,448,000
Structured credit fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments LPs/LLCs unfunded commitments	0
Investments in LPs/LLCs fair value	6,187,000	4,273,000
Long/Short commodities fund [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investments LPs/LLCs unfunded commitments	0
Investments in LPs/LLCs fair value	$ 12,094,000	$ 11,476,000

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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

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

The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments).

+ 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 (c)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=SL6742756-110258

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