Revenue from Contracts with Customers - Additional Information (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($) item	Jan. 31, 2018 USD ($)
Disaggregation of Revenue [Line Items]
Lease rent receivables past due	$ 4.1
Maintenance reserve receivables past due	$ 3.5
Number of performance obligations identified | item	1
Unbilled revenue associated with outstanding contracts	$ 0.7
Other Assets
Disaggregation of Revenue [Line Items]
Unbilled revenue associated with outstanding contracts		$ 0.4