Lessor Leases - Operating Lease Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Operating Leased Assets [Line Items]
Rental income	$ 2,896	$ 2,999	$ 9,548	$ 8,800
Total property and equipment, net	54,877		54,877		$ 51,500
Accumulated depreciation and amortization	111,244		111,244		100,789
Depreciation	$ 4,500	3,700	$ 12,900	11,000
Minimum
Operating Leased Assets [Line Items]
Term of Contract ( in years )	1 year		1 year
Maximum
Operating Leased Assets [Line Items]
Term of Contract ( in years )	7 years		7 years
Equipment
Operating Leased Assets [Line Items]
Total property and equipment, net	$ 2,300		$ 2,300		2,600
Accumulated depreciation and amortization	1,500		1,500		$ 1,200
Depreciation	$ 200	$ 200	$ 500	$ 300