Summary of Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Number of shares
Number of shares, Options outstanding, beginning of year	1,961	2,565	3,561
Number of shares, Granted	651	553	470
Number of shares, Exercised	(546)	(786)	(1,293)
Number of shares, Expired or Forfeited	(32)	(371)	(173)
Number of shares, Options outstanding, end of year	2,034	1,961	2,565
Number of shares, Options exercisable, end of year	728	1,001	1,828
Weighted average exercise price
Weighted average exercise price, Options outstanding, beginning of year	$ 8.20	$ 8.20	$ 6.53
Weighted average exercise price, Granted	$ 11.71	$ 9.88	$ 9.27
Weighted average exercise price, Exercised	$ 6.56	$ 7.54	$ 3.76
Weighted average exercise price, Expired or Forfeited	$ 14.06	$ 12.10	$ 9.83
Weighted average exercise price, Options outstanding, end of year	$ 9.67	$ 8.20	$ 8.20
Weighted average exercise price, Options exercisable, end of year	$ 7.92	$ 6.92	$ 8.18

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.

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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.

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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.

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Weighted average price of options that were either forfeited or expired.

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

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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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