Other Noncurrent Assets - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2018
Other Assets Non Current [Line Items]
Notes receivable			$ 2,600,000
City Of Henderson
Other Assets Non Current [Line Items]
Notes receivable	$ 3,100,000
Annual interest rate	6.00%
City Of Henderson | Notes Payable
Other Assets Non Current [Line Items]
Debt instrument expiry year	2036
OPA | City of Henderson Redevelopment Agency
Other Assets Non Current [Line Items]
Tax increment reimbursement percentage		75.00%
Aggregate amount of tax increment reimbursement receipts		$ 3,100,000
OPA | Maximum | City of Henderson Redevelopment Agency
Other Assets Non Current [Line Items]
Reimbursement revenue		$ 209,000,000