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Commitments and Contingencies (Details) - USD ($)	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Commitments and Contingencies
Co-investment commitments in partnership		$ 94,900,000
Consolidated Affiliates
Commitments and Contingencies
Contingent liability		21,700,000
Expected payments of contingent liability		8,900,000
Present value of expected payments of contingent liabilities		8,100,000
Consolidated Affiliates | Scenario, Forecast
Commitments and Contingencies
Expected payments of contingent liability	$ 1,600,000
Equity Method Investee
Commitments and Contingencies
Contingent liability		$ 170,000,000
Equity Method Investee | Scenario, Forecast
Commitments and Contingencies
Expected payments of contingent liability	$ 0
Third Avenue Focused Credit Fund | Affiliated Entity | Third Avenue
Commitments and Contingencies
Loss contingency reserve			$ 15,000,000

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- Definition

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- Definition

The amount that the entity agreed to co-invest in certain investment partnerships where the entity serves as the general partner.

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- Definition

Other Commitment Expected Payments

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- Definition

Other Commitment Present Value of Expected Payments

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- Definition

Amount of loss contingency liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

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- Definition

Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

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No definition available.

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