Stock Plans - Summary of Stock Option Activity (Detail) (USD $)	9 Months Ended
Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding Beginning balance, Shares	1,695,380
Granted, Shares	138,519
Exercised, Shares	(176,937)
Forfeited, Shares	(23,524)
Expired, Shares	(1,071)
Outstanding Ending balance, Shares	1,632,367
Exercisable Ending balance, Shares	1,161,518
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Outstanding Beginning balance, Weighted Average Exercise Price	$ 34.55
Granted, Weighted Average Exercise Price	$ 51.69
Exercised, Weighted Average Exercise Price	$ 36.59
Forfeited, Weighted Average Exercise Price	$ 38.82
Expired, Weighted Average Exercise Price	$ 45.68
Outstanding Ending balance, Weighted Average Exercise Price	$ 35.71
Exercisable Ending balance, Weighted Average Exercise Price	$ 31.64

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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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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-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.

+ References

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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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-Publisher FASB

-Name Accounting Standards Codification

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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.

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-Publisher FASB

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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 price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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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 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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-Name Regulation S-X (SX)

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