Fair Value Measurements - Narrative (Details)	6 Months Ended
Jun. 30, 2018
Minimum
Carrying amounts and estimated fair values of the financial instruments
Estimated liquidation period of underlying assets of the funds	1 year
Maximum
Carrying amounts and estimated fair values of the financial instruments
Estimated liquidation period of underlying assets of the funds	10 years

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.

No definition available.

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