Schedule of Range of Exercise Prices for Outstanding Options (Detail) (USD $)	6 Months Ended
Jun. 30, 2012
$14.24-$19.29
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Prices, Lower Limit	$ 14.24
Range of Prices, Upper Limit	$ 19.29
Options Outstanding	368,405
Weighted Average Remaining Contractual Life (Years)	5 years 8 months 12 days
$20.53-$27.24
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Prices, Lower Limit	$ 20.53
Range of Prices, Upper Limit	$ 27.24
Options Outstanding	235,712
Weighted Average Remaining Contractual Life (Years)	7 years
$30.07-$36.10
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Prices, Lower Limit	$ 30.07
Range of Prices, Upper Limit	$ 36.10
Options Outstanding	210,454
Weighted Average Remaining Contractual Life (Years)	4 years 7 months 6 days
$45.83-$60.11
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Prices, Lower Limit	$ 45.83
Range of Prices, Upper Limit	$ 60.11
Options Outstanding	209,594
Weighted Average Remaining Contractual Life (Years)	9 years 2 months 12 days

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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 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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

+ Details

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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

Reference 2: 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.

+ Details

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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

+ Details

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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

+ Details

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