Stock Incentive Plans - Summary of Information Concerning Stock Option Awards (Detail) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Shares, Options outstanding at beginning of year	533,524	640,050	586,020
Shares, Assumed from acquisition	805,507	274,964	627,808
Shares, Exercised	(690,973)	(69,429)	(182,188)
Shares, Forfeited	(79,224)	(312,061)	(391,590)
Shares, Options outstanding and exercisable at end of year	568,834	533,524	640,050
Weighted Average Price per Share, Options outstanding at beginning of year	$ 11.50	$ 13.21	$ 14.93
Weighted Average Price per Share, Assumed from acquisition	$ 7.39	$ 11.16	$ 10.41
Weighted Average Price per Share, Exercised	$ 7.75	$ 7.46	$ 8.87
Weighted Average Price per Share, Forfeited	$ 21.40	$ 15.58	$ 13.32
Weighted Average Price per Share, Options outstanding and exercisable at end of year	$ 8.86	$ 11.50	$ 13.21

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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.

+ 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)

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The addition or reduction in the number of reserved shares that could potentially be issued under the option plan attributable to reasons other than grants, exercises, forfeitures, and expirations during the reporting period.

+ References

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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 price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average price at which grantees could acquire or could have acquired the underlying shares with respect to any other type of change in shares reserved for issuance.

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

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