Summary Information of Stock Options (Detail) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options, Outstanding at January 1, 2014	882,416
Number of Options, Granted	55,981
Number of Options, Granted-Replacement Options	821,282
Number of Options, Exercised	(697,154)
Number of Options, Terminated	(8,090)
Number of Options, Outstanding at December 31, 2014	1,054,435	882,416
Number of Options, Exercisable at December 31, 2014	906,719
Weighted-Average Exercise Price, Outstanding at January 1, 2014	$ 102.74
Weighted-Average Exercise Price, Granted	$ 121.00	$ 108.24	$ 69.12
Weighted-Average Exercise Price, Granted-Replacement Options	$ 56.66
Weighted-Average Exercise Price, Exercised	$ 59.98
Weighted-Average Exercise Price, Terminated	$ 45.12
Weighted-Average Exercise Price, Outstanding at December 31, 2014	$ 96.53	$ 102.74
Weighted-Average Exercise Price, Exercisable at December 31, 2014	$ 95.67
Weighted-Average Remaining Contractual Life (years), Outstanding at December 31, 2014	3 years 6 months
Weighted-Average Remaining Contractual Life (years), Exercisable at December 31, 2014	2 years 9 months 18 days

Share based compensation arrangement by share based payment award options replacement in period.

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Share based compensation arrangements by share based payment award options replacement in period weighted average exercise price.

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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

-Paragraph 2

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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

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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-Publisher FASB

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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 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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- Definition

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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