Fair Value Measurements - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short term investments	$ 0.7	$ 22.0
Clinton Group
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short term investments	0.4	19.5
Decrease in short-term investment balance	19.1
Redemptions	18.7
GBAM Fund
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short term investments	0.1
Unrealized appreciation on swaps	1.2
Unrealized depreciation on swaps	1.1
Other income (expense), net \| Clinton Group
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities, unrealized holding loss	$ 0.4	4.5
Performance fees		$ 0.5

Redemption Of Trading Securities

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- Definition

Short-term Investments, Period Increase (Decrease)

+ References

No definition available.

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- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable for professional fees, such as for legal and accounting services received.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.15(5))
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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

This element represents the excess of the cost (face amount, notional amount) of an investment (security, contract) over its fair value which deficiency has not been recognized in earnings of the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
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- Definition

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- Definition

Amount of investments including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.

+ References

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- Definition

Amount of unrealized holding loss before gain recognized in the income statement for investments in trading securities.

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