Stock-Based Compensation - Summary of Activity under Stock Plan (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Awards Outstanding, Beginning Balance	998,160
Number of Awards, granted	282,200
Number of Awards, exercised	(9,968)
Number of Awards, forfeited	(4,644)
Number of Awards, expired	(36,268)
Number of Awards, Outstanding, Ending Balance	1,229,480
Number of Awards, exercisable	810,457
Weighted-Average Exercise Price Outstanding, Beginning Balance	$ 85.01
Weighted-Average Exercise Price, granted	$ 64.33
Weighted-Average Exercise Price, exercised	$ 51.57
Weighted-Average Exercise Price, forfeited	$ 68.73
Weighted-Average Exercise Price, expired	$ 94.14
Weighted-Average Exercise Price Outstanding, Ending Balance	$ 80.32
Weighted-Average Exercise Price Outstanding, exercisable	$ 86.86
Weighted-Average Remaining Contractual Term, Ending Balance	7 years
Weighted-Average Remaining Contractual Term, exercisable	6 years
Aggregate Intrinsic Value, Ending Balance	$ 3,515
Aggregate Intrinsic Value, exercisable	$ 2,141

Share Based Compensation Arrangement By Share Based Payment Award Options Exercised

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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.

+ References

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- Definition

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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- Definition

Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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- Definition

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.

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

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

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- Definition

The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including 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 remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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 of the plan that expired.

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No definition available.

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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 can acquire the shares reserved for issuance on stock options awarded.

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