Related Party Transactions - Summary of Components of Due to Affiliates (Parenthetical) (Detail)	9 Months Ended
Sep. 30, 2019
Blackstone Advisory Partners L.P. [Member]
Related Party Transaction [Line Items]
Commission and fees, threshold percentage on gross proceeds from sale of share	8.75%

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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