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Fair Value Measurement (Investments in LLCs and Limited Partnerships) (Details) - USD ($) | Jun. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Fair Value | $ 297,762,000 | $ 230,889,000
Equities | Mortgage fund |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Unfunded Commitments | 0 |
Fair Value | 20,257,000 | 0
Investment in unconsolidated subsidiaries |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Fair Value | 277,505,000 | 210,759,000
Investment in unconsolidated subsidiaries | Private debt funds |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Unfunded Commitments | 4,945,000 |
Fair Value | 26,174,000 | 42,206,000
Investment in unconsolidated subsidiaries | Long equity fund |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Unfunded Commitments | 0 |
Fair Value | 7,712,000 | 7,847,000
Investment in unconsolidated subsidiaries | Long/short equity funds |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Unfunded Commitments | 0 |
Fair Value | 32,134,000 | 31,352,000
Investment in unconsolidated subsidiaries | Non-public equity funds |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Unfunded Commitments | 78,693,000 |
Fair Value | 109,337,000 | 100,062,000
Investment in unconsolidated subsidiaries | Multi-strategy fund of funds |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Unfunded Commitments | 0 |
Fair Value | 9,357,000 | 9,100,000
Investment in unconsolidated subsidiaries | Credit fund |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Unfunded Commitments | 0 |
Fair Value | 18,075,000 | 6,561,000
Investment in unconsolidated subsidiaries | Long/short commodities fund |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Unfunded Commitments | 0 |
Fair Value | 13,380,000 | 13,025,000
Investment in unconsolidated subsidiaries | Strategy focused fund |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Unfunded Commitments | 19,247,000 |
Fair Value | 61,336,000 | 606,000
Other investments | Mortgage fund |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Fair Value | $ 0 | $ 20,130,000

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- Definition Fair value of investment in certain entities that calculate net asset value per share. Includes, but is not limited to, by unit, membership interest, or other ownership interest. Investment includes, but is not limited to, investment in certain hedge funds, venture capital funds, private equity funds, real estate partnerships or funds. Excludes measurement of net asset value as estimate of fair value. + 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 + Details
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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 + Details
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