Leases - Components of Net Investment in Sales-Type Leases (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Sales Type Leases Net Investment In Leases [Abstract]
Current minimum lease payments receivable (included in other receivables)	$ 9,349	$ 11,339
Non-current minimum lease payments receivable (included in other assets)	1,494	1,670
Total minimum lease payments receivable	10,843	13,009
Less: Current unearned revenue	573	631
Less: Non-current unearned revenue	343	473
Net investment in sales-type leases	$ 9,927	$ 11,905