Excess of issue price over par or stated value of the entity's capital stock and amounts received from other transactions involving the entity's stock or stockholders. Includes adjustments to additional paid in capital. Some examples of such adjustments include recording the issuance of debt with a beneficial conversion feature and certain tax consequences of equity instruments awarded to employees. Use this element for the aggregate amount of additional paid-in capital associated with common and preferred stock. For additional paid-in capital associated with only common stock, use the element additional paid in capital, common stock. For additional paid-in capital associated with only preferred stock, use the element additional paid in capital, preferred stock.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(30)(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Jan. 31, 2017	Dec. 31, 2016
Summary of Significant Accounting Policy [Line Items]
Retained earnings	$ 941,845		$ 921,942
ASU 2016-09 [Member]
Summary of Significant Accounting Policy [Line Items]
Increase in additional paid in capital		$ 100
Retained earnings		100
ASU 2016-09 [Member] \| Non-qualified Stock Options and RSUs [Member]
Summary of Significant Accounting Policy [Line Items]
Increase in deferred tax assets		$ 10