Net Income (Loss) Per Share of Common Stock - Additional Information (Detail)	9 Months Ended
Sep. 30, 2017
Class B And Class C Convert To Class A [Member]
Earnings Per Share Diluted [Line Items]
Class of common stock conversion ratio	100.00%

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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Balance Type:	na
Period Type:	duration