Supplemental Financial Information - Noncash Operating and Investing Activities (Parenthetical) (Detail) - shares	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Restricted Stock [Member]
Condensed Financial Statements, Captions [Line Items]
Number of shares of common stock withheld	131,698	129,456

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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Period Type:	duration