Lessor Leases - Sales-type Lease Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Leases [Abstract]
Sales-type lease revenues	$ 13,309	$ 7,533	$ 24,816	$ 17,390
Interest income on sales-type lease receivables	$ 399	$ 314	$ 808	$ 581