Benefit Plans - Summary of Stock Options and SARs Outstanding by Exercise Price Range (Detail) (USD $)	12 Months Ended
Dec. 31, 2014
20.01 - 30.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Awards Outstanding, Number of Shares	584,200
Awards Outstanding, Weighted Average Remaining Contractual Life	2 years 8 months 16 days
Awards Outstanding, Weighted Average Exercise Price	$ 25.207
Awards Exercisable, Number of Shares	584,200
Awards Exercisable, Weighted Average Exercise Price	$ 25.207
Range of exercise prices, lower range limit	$ 20.01
Range of exercise prices, upper range limit	$ 30.00
30.01 - 40.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Awards Outstanding, Number of Shares	2,674,903
Awards Outstanding, Weighted Average Remaining Contractual Life	4 years 8 months 12 days
Awards Outstanding, Weighted Average Exercise Price	$ 36.874
Awards Exercisable, Number of Shares	2,284,666
Awards Exercisable, Weighted Average Exercise Price	$ 36.567
Range of exercise prices, lower range limit	$ 30.01
Range of exercise prices, upper range limit	$ 40.00
40.01 - 50.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Awards Outstanding, Number of Shares	3,468,850
Awards Outstanding, Weighted Average Remaining Contractual Life	6 years 4 months 21 days
Awards Outstanding, Weighted Average Exercise Price	$ 44.135
Awards Exercisable, Number of Shares	1,874,558
Awards Exercisable, Weighted Average Exercise Price	$ 44.419
Range of exercise prices, lower range limit	$ 40.01
Range of exercise prices, upper range limit	$ 50.00
50.01 - 60.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Awards Outstanding, Number of Shares	180,825
Awards Outstanding, Weighted Average Remaining Contractual Life	2 years 18 days
Awards Outstanding, Weighted Average Exercise Price	$ 51.080
Awards Exercisable, Number of Shares	180,825
Awards Exercisable, Weighted Average Exercise Price	$ 51.080
Range of exercise prices, lower range limit	$ 50.01
Range of exercise prices, upper range limit	$ 60.00

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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- Definition

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

-Subparagraph (g)

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

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- Definition

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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- Definition

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

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(i)-(ii)

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

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- Definition

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

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(i)-(ii)

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

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- Definition

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

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (e)(1)

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

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- Definition

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

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (g)

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

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