Stock Options Outstanding (Detail) (USD $)	12 Months Ended
Dec. 31, 2011 Year
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Outstanding Options, Shares	2,439,360
Outstanding Options ,Weighted Average Remaining Contractual Life in Years	3.51
Outstanding Options, Weighted Average Exercise Price	$ 42.64
Exercisable Options, Shares	1,404,132
Exercisable Options, Weighted Average Exercise Price	$ 40.09
Range 1
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 15.15
Range of Exercise Prices, maximum	$ 19.67
Outstanding Options, Shares	393,436
Outstanding Options ,Weighted Average Remaining Contractual Life in Years	3.36
Outstanding Options, Weighted Average Exercise Price	$ 18.91
Exercisable Options, Shares	225,606
Exercisable Options, Weighted Average Exercise Price	$ 18.49
Range 2
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 19.68
Range of Exercise Prices, maximum	$ 32.15
Outstanding Options, Shares	311,340
Outstanding Options ,Weighted Average Remaining Contractual Life in Years	1.83
Outstanding Options, Weighted Average Exercise Price	$ 27.72
Exercisable Options, Shares	250,499
Exercisable Options, Weighted Average Exercise Price	$ 27.79
Range 3
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 32.16
Range of Exercise Prices, maximum	$ 45.23
Outstanding Options, Shares	267,747
Outstanding Options ,Weighted Average Remaining Contractual Life in Years	3.62
Outstanding Options, Weighted Average Exercise Price	$ 43.44
Exercisable Options, Shares	142,986
Exercisable Options, Weighted Average Exercise Price	$ 43.44
Range 4
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 45.24
Range of Exercise Prices, maximum	$ 48.26
Outstanding Options, Shares	255,025
Outstanding Options ,Weighted Average Remaining Contractual Life in Years	1.91
Outstanding Options, Weighted Average Exercise Price	$ 47.29
Exercisable Options, Shares	234,579
Exercisable Options, Weighted Average Exercise Price	$ 47.31
Range 5
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 48.27
Range of Exercise Prices, maximum	$ 48.85
Outstanding Options, Shares	292,112
Outstanding Options ,Weighted Average Remaining Contractual Life in Years	3.24
Outstanding Options, Weighted Average Exercise Price	$ 48.75
Exercisable Options, Shares	215,232
Exercisable Options, Weighted Average Exercise Price	$ 48.74
Range 6
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 48.86
Range of Exercise Prices, maximum	$ 49.41
Outstanding Options, Shares	270,807
Outstanding Options ,Weighted Average Remaining Contractual Life in Years	5.31
Outstanding Options, Weighted Average Exercise Price	$ 49.18
Exercisable Options, Shares	63,561
Exercisable Options, Weighted Average Exercise Price	$ 49.17
Range 7
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 49.42
Range of Exercise Prices, maximum	$ 53.07
Outstanding Options, Shares	170,434
Outstanding Options ,Weighted Average Remaining Contractual Life in Years	2.23
Outstanding Options, Weighted Average Exercise Price	$ 51.33
Exercisable Options, Shares	154,266
Exercisable Options, Weighted Average Exercise Price	$ 51.46
Range 8
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 53.08
Range of Exercise Prices, maximum	$ 60.14
Outstanding Options, Shares	154,426
Outstanding Options ,Weighted Average Remaining Contractual Life in Years	2.56
Outstanding Options, Weighted Average Exercise Price	$ 54.32
Exercisable Options, Shares	117,403
Exercisable Options, Weighted Average Exercise Price	$ 53.66
Range 9
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 60.15
Range of Exercise Prices, maximum	$ 60.65
Outstanding Options, Shares	324,033
Outstanding Options ,Weighted Average Remaining Contractual Life in Years	6.32
Outstanding Options, Weighted Average Exercise Price	$ 60.37

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 Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: 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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- 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 Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(c)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: 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 Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(a, b)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: 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

The weighted-average period remaining as of the balance sheet date until option expiration pertaining to the outstanding stock options for all option plans in the customized range of exercise prices, which may be expressed in a variety of ways (for example, years, months).

+ 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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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

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