Investments of Operating Entities and Consolidated Funds - Indirect Concentration of the Underlying Investments Held by Consolidated Funds (Details) $ in Thousands	Dec. 31, 2018 USD ($) investments	Dec. 31, 2017 USD ($) investments
Investment [Line Items]
Concentration of risk, number of investments \| investments	1	1
Equity Securities \| Linkem \| ITALY \| 517210 Wireless Telecommunications Carriers (except Satellite)
Investment [Line Items]
Percentage of Equity	8.36%	7.52%
Market Value \| $	$ 66,439	$ 56,271

Value of the investment at close of period. For schedules of investments that are categorized, the value would be aggregated by category. For investment in and advances to affiliates, if operations of any controlled companies are different in character from those of the company, group such affiliates within divisions and by type of activities.

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Balance Type:	debit
Period Type:	instant