Stock Options Issued under Stock Option Program Awards (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Limit	$ 13
Range of Exercise Prices, Upper Limit	$ 53
Outstanding - Number of Stock Options (in millions)	0.7
Outstanding - Weighted Average Exercise Price (per unit)	$ 36
Outstanding - Weighted Average Remaining Life	6 years
Exercisable - Number of Stock Options (in millions)	0.3
Exercisable - Weighted Average Exercise Price (per unit)	$ 32
Exercisable - Weighted Average Remaining Life	4 years
Range 2
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Limit	$ 13
Range of Exercise Prices, Upper Limit	$ 22
Outstanding - Number of Stock Options (in millions)	0
Outstanding - Weighted Average Exercise Price (per unit)	$ 17
Outstanding - Weighted Average Remaining Life	1 year
Exercisable - Number of Stock Options (in millions)	0
Exercisable - Weighted Average Exercise Price (per unit)	$ 17
Exercisable - Weighted Average Remaining Life	1 year
Range 3
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Limit	$ 23
Range of Exercise Prices, Upper Limit	$ 35
Outstanding - Number of Stock Options (in millions)	0.5
Outstanding - Weighted Average Exercise Price (per unit)	$ 32
Outstanding - Weighted Average Remaining Life	5 years
Exercisable - Number of Stock Options (in millions)	0.3
Exercisable - Weighted Average Exercise Price (per unit)	$ 30
Exercisable - Weighted Average Remaining Life	4 years
Range 4
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Limit	$ 36
Range of Exercise Prices, Upper Limit	$ 53
Outstanding - Number of Stock Options (in millions)	0.2
Outstanding - Weighted Average Exercise Price (per unit)	$ 45
Outstanding - Weighted Average Remaining Life	8 years
Exercisable - Number of Stock Options (in millions)	0
Exercisable - Weighted Average Exercise Price (per unit)	$ 41
Exercisable - Weighted Average Remaining Life	6 years

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.

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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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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Number of options outstanding, including both vested and non-vested options.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

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

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-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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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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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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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.

+ 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

-Subparagraph (g)

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

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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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-Section 50

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