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Stock-Based Compensation - Summary of Stock Option Activity, SOSARS (Detail) (SOSARs [Member], USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
SOSARs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Outstanding	2,121,454	2,298,288
Granted	361,923	364,114
Exercised	(435,562)	(500,074)
Canceled / forfeited	(73,901)	(12,000)
Ending Balance, Outstanding	1,973,914	2,150,328
Beginning Balance, Weighted Average Exercise Price, Outstanding	$ 12.93	$ 12.35
Weighted Average Exercise Price, Granted	$ 18.36	$ 15.23
Weighted Average Exercise Price, Exercised	$ 12.63	$ 12.06
Weighted Average Exercise Price, Canceled	$ 16.25	$ 14.96
Ending Balance, Weighted Average Exercise Price, Outstanding	$ 13.87	$ 12.94
Weighted average grant date fair value per share	$ 5.64	$ 4.94
Aggregate grant date fair value	$ 2,042	$ 1,797
Black-Scholes assumptions
Dividend yield	2.18%	2.31%
Risk free rate of return	0.99%	1.02%
Volatility	39.62%	41.48%
Expected life	6 years	6 years

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Share based compensation arrangement by share based payment award options grant date fair value.

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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-Publisher FASB

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Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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Weighted average expected volatility rate of share-based compensation awards.

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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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Gross 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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