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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.

+ 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), d(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

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

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- Definition

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 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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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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Stock-Based Compensation Information related to stock options outstanding (Details) (USD $)	May 31, 2012	May 31, 2011	May 31, 2010	May 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of exercisable options (in shares)	2,105,702	1,945,207	1,838,530	1,914,710
$20.29 - 31.00 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding (in shares)	1,725,722
Average Remaining Option Life (In years)	7.50
Weighted Average Exercise Price, Outstanding Options (in dollars per share)	26.22
Number Exercisable (in shares)	176,768
Weighted Average Exercise Price, Exercisable Options (in dollars per share)	26.97
$31.01 - 34.27 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding (in shares)	1,279,826
Average Remaining Option Life (In years)	8.61
Weighted Average Exercise Price, Outstanding Options (in dollars per share)	33.99
Number Exercisable (in shares)	60,390
Weighted Average Exercise Price, Exercisable Options (in dollars per share)	33.50
$34.28 - 39.36 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding (in shares)	2,410,094
Average Remaining Option Life (In years)	6.77
Weighted Average Exercise Price, Outstanding Options (in dollars per share)	37.49
Number Exercisable (in shares)	622,774
Weighted Average Exercise Price, Exercisable Options (in dollars per share)	38.69
$39.37 - 50.47 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding (in shares)	2,193,475
Average Remaining Option Life (In years)	2.48
Weighted Average Exercise Price, Outstanding Options (in dollars per share)	42.51
Number Exercisable (in shares)	1,245,770
Weighted Average Exercise Price, Exercisable Options (in dollars per share)	42.65
$20.29 - 50.47 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding (in shares)	7,609,117
Average Remaining Option Life (In years)	6.01
Weighted Average Exercise Price, Outstanding Options (in dollars per share)	36.04
Number Exercisable (in shares)	2,105,702
Weighted Average Exercise Price, Exercisable Options (in dollars per share)	39.90
Minimum [Member] \| $20.29 - 31.00 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Exercise Price, Outstanding Options (in dollars per share)	20.29
Minimum [Member] \| $31.01 - 34.27 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Exercise Price, Outstanding Options (in dollars per share)	31.01
Minimum [Member] \| $34.28 - 39.36 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Exercise Price, Outstanding Options (in dollars per share)	34.28
Minimum [Member] \| $39.37 - 50.47 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Exercise Price, Outstanding Options (in dollars per share)	39.37
Minimum [Member] \| $20.29 - 50.47 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Exercise Price, Outstanding Options (in dollars per share)	20.29
Maximum [Member] \| $20.29 - 31.00 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Exercise Price, Outstanding Options (in dollars per share)	31.00
Maximum [Member] \| $31.01 - 34.27 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Exercise Price, Outstanding Options (in dollars per share)	34.27
Maximum [Member] \| $34.28 - 39.36 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Exercise Price, Outstanding Options (in dollars per share)	39.36
Maximum [Member] \| $39.37 - 50.47 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Exercise Price, Outstanding Options (in dollars per share)	50.47
Maximum [Member] \| $20.29 - 50.47 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Exercise Price, Outstanding Options (in dollars per share)	50.47