Share-Based Compensation - Activity in Company's Plan (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding at January 1, 2013, Number of Shares	32,150
Exercised, Number of Shares	(19,150)
Outstanding (exercisable and vested) at December 31, 2013, Number of Shares	13,000
Exercisable at December 31, 2013, Number of Shares	13,000
Outstanding at January 1, 2013, Weighted Average Exercise Price per Share	$ 40.93
Exercised, Weighted Average Exercise Price per Share	$ 41.59
Outstanding (exercisable and vested) at December 31, 2013, Weighted Average Exercise Price per Share	$ 39.95
Exercisable at December 31, 2013, Weighted Average Exercise Price per Share	$ 39.95
Outstanding (exercisable and vested), Weighted Average Remaining Contractual Term	3 years 7 months 6 days
Exercisable, Weighted Average Remaining Contractual Term	3 years 7 months 6 days
Outstanding (exercisable and vested), Aggregate Intrinsic Value	$ 432
Exercisable, Aggregate Intrinsic Value	$ 432

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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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.

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-Section 50

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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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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of fully vested and expected to vest options that are exercisable.

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The number of exercisable share options (fully vested and expected to vest) that may be converted as of the balance sheet date.

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As of the balance sheet date, the weighted-average exercise price (at which grantees can acquire the shares reserved for issuance) for exercisable stock options that are fully vested or expected to vest.

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

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

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