Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	Nov. 30, 2017	May 31, 2017
Commitments to purchase capital assets	$ 4.5	$ 7.4

Amount of contractual obligation, including but not limited to, long-term debt, capital lease obligations, operating lease obligations, purchase obligations, and other commitments.

No definition available.

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