Property, Plant and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jan. 01, 2019	Dec. 31, 2018
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	$ 278,484		$ 278,484			$ 276,288
Less: accumulated depreciation and amortization	(193,994)		(193,994)			(186,799)
Total property, plant, and equipment, net	84,490		84,490		$ 81,421	89,489
Depreciation expense	7,800	$ 7,500	23,000	$ 22,300
Land
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	634		634			644
Buildings
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	4,046		4,046			24,558
Furniture and fixtures
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	13,332		13,332			13,121
Machinery and equipment
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	26,603		26,603			27,452
Equipment leased to third parties under operating leases
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	29,943		29,943			30,093
Leasehold improvements
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	129,029		129,029			111,247
Computers and software
Property, Plant and Equipment, Net
Total property, plant, and equipment, gross	$ 74,897		$ 74,897			$ 69,173