Stock Options Outstanding (Detail) (USD $)	12 Months Ended
Dec. 31, 2011 Year
Range 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Prices lower limit	$ 9.90
Exercise Prices upper limit	$ 14.25
Number Outstanding	613,158
Weighted Average Remaining Contractual Life	6.25
Weighted Average Exercise Price	$ 10.77
Number Option Exercisable	246,158
Weighted Average Exercise Price	$ 12.00
Range 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Prices lower limit	$ 14.26
Exercise Prices upper limit	$ 21.51
Number Outstanding	592,625
Weighted Average Remaining Contractual Life	6.83
Weighted Average Exercise Price	$ 16.79
Number Option Exercisable	326,925
Weighted Average Exercise Price	$ 17.87
Range 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Prices lower limit	$ 21.52
Exercise Prices upper limit	$ 22.33
Number Outstanding	976,390
Weighted Average Remaining Contractual Life	7.06
Weighted Average Exercise Price	$ 22.15
Number Option Exercisable	329,838
Weighted Average Exercise Price	$ 21.82
Range 4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Prices lower limit	$ 22.34
Exercise Prices upper limit	$ 23.21
Number Outstanding	614,000
Weighted Average Remaining Contractual Life	6.14
Weighted Average Exercise Price	$ 22.57
Number Option Exercisable	224,000
Weighted Average Exercise Price	$ 22.53
Range 5
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Prices lower limit	$ 23.22
Exercise Prices upper limit	$ 29.73
Number Outstanding	845,350
Weighted Average Remaining Contractual Life	4.21
Weighted Average Exercise Price	$ 26.11
Number Option Exercisable	801,350
Weighted Average Exercise Price	$ 26.11
Range 6
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Prices lower limit	$ 29.74
Exercise Prices upper limit	$ 29.98
Number Outstanding	839,860
Weighted Average Remaining Contractual Life	8.71
Weighted Average Exercise Price	$ 29.98
Range 7
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Prices lower limit	$ 29.99
Exercise Prices upper limit	$ 38.46
Number Outstanding	623,400
Weighted Average Remaining Contractual Life	8.42
Weighted Average Exercise Price	$ 37.77
Number Option Exercisable	70,000
Weighted Average Exercise Price	$ 34.80
Range 8
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Prices lower limit	$ 38.47
Exercise Prices upper limit	$ 64.41
Number Outstanding	756,500
Weighted Average Remaining Contractual Life	9.80
Weighted Average Exercise Price	$ 58.82

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

+ 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)(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

-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 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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- 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

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