SHARE-BASED AWARDS AND OPTIONS - Stock Options Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Aug. 31, 2016	Aug. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	72,733	72,393
Share-based compensation expense	$ 7,619	$ 6,467
Aggregate intrinsic value of stock options exercised	6,100	2,700
Total unrecognized compensation cost	$ 3,700
Employee stock option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair market value (as a percentage)	100.00%
Stock option term	10 years
Share-based compensation expense	$ 400	$ 200
Total unrecognized compensation cost, weighted average period	2 years 1 month 6 days
Stock Option Plan 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value for each option granted (in dollars per share)	$ 21.87	$ 15.60
Granted Before Fiscal 2015 \| Employee stock option \| Performance period. year one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of award vesting rights	25.00%
Granted Before Fiscal 2015 \| Employee stock option \| Performance period, year two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of award vesting rights	25.00%
Granted Before Fiscal 2015 \| Employee stock option \| Performance period, year three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of award vesting rights	25.00%
Granted Before Fiscal 2015 \| Employee stock option \| Performance period, year four
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of award vesting rights	25.00%
Granted Fiscal 2015 \| Employee stock option \| Performance period. year one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of award vesting rights	33.00%
Granted Fiscal 2015 \| Employee stock option \| Performance period, year two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of award vesting rights	33.00%
Granted Fiscal 2015 \| Employee stock option \| Performance period, year three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of award vesting rights	33.00%

Share-based Compensation Arrangement by Share-based Payment Award, Award Fair Market Value Percent

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 14.F)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 14
-Section F

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, 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
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

+ 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 (d)(2)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Gross number of share options (or share units) granted during the period.

+ References

No definition available.

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- Definition

Percentage of vesting of share-based compensation awards.

+ 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 (a)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Period from grant date that an equity-based award expires, 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
-Topic 718
-SubTopic 10
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-Paragraph 2
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- Definition

Weighted average grant-date fair value of non-vested options outstanding.

+ References

No definition available.

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