Reconciliation of Numerator and Denominator of Basic and Diluted Earnings Per Share (Parenthetical) (Detail) - shares	3 Months Ended
Aug. 31, 2017	Aug. 31, 2016
Restricted shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares excluded from the calculation of diluted earnings per share	43,380	0
Stock appreciation rights (SARs)
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares excluded from the calculation of diluted earnings per share	600,000	1,170,000

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Name:	us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration