Stock Plans - Schedule of Exercise Price Ranges, Characteristics of Outstanding Stock Options (Detail) (USD $)	12 Months Ended
Dec. 31, 2014
$17.83-$29.33
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 17.83
Range of Exercise Prices, maximum	$ 29.33
Stock Options Outstanding, Shares	541,669
Stock Options Outstanding, Weighted-Average Exercise Price	$ 21.71
Stock Options Outstanding, Weighted-Average Remaining Life, in years	4 years 7 months
Stock Options Exercisable, Shares	541,669
Exercisable, Weighted-Average Exercise Price	$ 21.71
Stock Options Exercisable, Weighted-Average Remaining Life, in years	4 years 7 months
$33.55-$40.88
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 33.55
Range of Exercise Prices, maximum	$ 40.88
Stock Options Outstanding, Shares	507,688
Stock Options Outstanding, Weighted-Average Exercise Price	$ 37.14
Stock Options Outstanding, Weighted-Average Remaining Life, in years	4 years 8 months 0 days
Stock Options Exercisable, Shares	360,801
Exercisable, Weighted-Average Exercise Price	$ 37.33
Stock Options Exercisable, Weighted-Average Remaining Life, in years	3 years 8 months 2 days
$41.26 – $51.69
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 41.26
Range of Exercise Prices, maximum	$ 51.69
Stock Options Outstanding, Shares	569,204
Stock Options Outstanding, Weighted-Average Exercise Price	$ 47.83
Stock Options Outstanding, Weighted-Average Remaining Life, in years	6 years 1 month 0 days
$17.83 – $51.69
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 17.83
Range of Exercise Prices, maximum	$ 51.69
Stock Options Outstanding, Shares	1,618,561
Stock Options Outstanding, Weighted-Average Exercise Price	$ 35.74
Stock Options Outstanding, Weighted-Average Remaining Life, in years	5 years 2 months 10 days
$41.26 – $48.95
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 41.26
Range of Exercise Prices, maximum	$ 48.95
Stock Options Exercisable, Shares	245,242
Exercisable, Weighted-Average Exercise Price	$ 45.17
Stock Options Exercisable, Weighted-Average Remaining Life, in years	3 years 0 months 6 days
$17.83 – $48.95
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 17.83
Range of Exercise Prices, maximum	$ 48.95
Stock Options Exercisable, Shares	1,147,712
Exercisable, Weighted-Average Exercise Price	$ 31.63
Stock Options Exercisable, Weighted-Average Remaining Life, in years	4 years 0 months 18 days

Weighted average exercise price as of the balance sheet date for those equity-based payment arrangements exercisable and outstanding.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

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-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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The number of shares reserved for issuance pertaining to the outstanding exercisable stock options as of the balance sheet date in the customized range of exercise prices for which the market and performance vesting condition has been satisfied.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(iii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

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The weighted average price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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