Commitments and Contingencies - Additional Information (Detail)	9 Months Ended
Sep. 30, 2018 LegalMatter
Loss Contingencies [Line Items]
Number of pending legal proceedings that would have an effect on consolidated financial position, results of operations, or cash flows	0

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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