Face (par) amount of debt instrument at time of issuance.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Debt - Unsecured Senior Notes - Narrative (Details) - USD ($)	May 31, 2019	Apr. 30, 2015
Unsecured senior notes \| 5.50% Senior Notes
Debt Instrument [Line Items]
Debt instrument, face amount		$ 55,000,000
Debt instrument, interest rate		5.50%
Revolving Credit Facility and Senior Notes \| Subsequent Event
Debt Instrument [Line Items]
Debt instrument, interest rate	7.50%