Concentrations of Risk - Additional Information (Detail)	May 31, 2017 USD ($)
Risks and Uncertainties [Abstract]
Maximum insurance available to depositors under the FDIC's general deposit insurance rules	$ 250,000
Cash balances not federally insured	$ 83,400,000

The amount of cash deposited in financial institutions as of the balance sheet date that is insured by the Federal Deposit Insurance Corporation.

No definition available.

Name:	us-gaap_CashFDICInsuredAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant