Changes in Equity (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Aug. 31, 2012	Aug. 31, 2011
Shareholders Equity [Line Items]
Beginning Balance	$ 747,437
Comprehensive income	39,585	26,006
Common shares issued	10,855
Stock-based compensation	3,548
Cash dividends declared	(9,043)
Ending Balance	792,382
Additional Paid-in Capital
Shareholders Equity [Line Items]
Beginning Balance	192,338
Common shares issued	10,855
Stock-based compensation	3,548
Ending Balance	206,741
Accumulated Other Comprehensive Income (Loss)
Shareholders Equity [Line Items]
Beginning Balance	(20,387)
Comprehensive income	4,609
Ending Balance	(15,778)
Retained Earnings
Shareholders Equity [Line Items]
Beginning Balance	525,223
Comprehensive income	33,962
Cash dividends declared	(9,043)
Ending Balance	550,142
Parent
Shareholders Equity [Line Items]
Beginning Balance	697,174
Comprehensive income	38,571
Common shares issued	10,855
Stock-based compensation	3,548
Cash dividends declared	(9,043)
Ending Balance	741,105
Noncontrolling Interest
Shareholders Equity [Line Items]
Beginning Balance	50,263
Comprehensive income	1,014
Ending Balance	$ 51,277

This element represents the amount of recognized equity-based compensation during the period, that is, the amount recognized as expense in the income statement (or as asset if compensation is capitalized). Alternate captions include the words "stock-based compensation".

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 20

-Section 55

-Paragraph 13

-URI http://asc.fasb.org/extlink&oid=6576910&loc=d3e11178-113907

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64

-Subparagraph 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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 35

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415241&loc=d3e4534-113899

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A91

-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 5: 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 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 20

-Section 55

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=6576910&loc=d3e11149-113907

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 39

-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

- Definition

The change in equity [net assets] of a business enterprise during a period from transactions and other events and circumstances from non-owner sources which are attributable to the economic entity, including both controlling (parent) and noncontrolling interests. It includes all changes in equity during a period except those resulting from investments by owners and distributions to owners, including any and all transactions which are directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent.

+ References+ Details

- Definition

Equity impact of cash dividends declared by an entity during the period for all classes of stock (common, preferred, etc.). This element includes paid and unpaid dividends declared during the period.

+ References+ Details

- Definition

Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

+ References+ Details

- Definition

Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

+ References+ Details