Stock Plans and Other Incentives - Option Activity and Other Plan Data (Detail) - $ / shares	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Outstanding at beginning of period, Options	530,000	547,500
Granted, Options	0	0
Exercised, Options	(285,000)	(17,500)
Forfeited/cancelled/expired, Options	0	0
Outstanding at end of period, Options	245,000	530,000
Options exercisable at end of period, Options	237,000	518,000
Outstanding at beginning of period, Weighted-Average Exercise Price	$ 9.64	$ 9.61
Granted, Weighted-Average Exercise Price	0	0
Exercised, Weighted-Average Exercise Price	(10.30)	(8.74)
Forfeited/cancelled/expired, Weighted-Average Exercise Price	0	0
Outstanding at end of period, Weighted-Average Exercise Price	8.88	9.64
Options exercisable at end of period, Weighted-Average Exercise Price	$ 8.56	$ 9.44

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

+ References

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- Definition

For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)-(4)
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Weighted average price of options that were either forfeited or expired.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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- Definition

Gross number of share options (or share units) granted during the period.

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No definition available.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Number of share options (or share units) exercised during the current period.

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