Contingent Liabilities and Commitments - Summary of Progression of Liabilities (Detail) - Tank Replacement Costs $ in Thousands	9 Months Ended
Feb. 28, 2019 USD ($)
Loss Contingencies [Line Items]
Beginning balance	$ 13,000
Payments	2,000
Ending balance	$ 11,000

Amount of cash outflow reducing loss contingency liability.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration