Receivables - Receivables (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 8,731	$ 8,957
Allowance for bad debts	(26)	(26)
Receivables, net	8,705	8,931
Receivables and accrued interest
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	613	1,505
Notes receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 8,118	$ 7,452
Average interest rates	4.97%	4.94%