Goodwill and Intagible Assets - Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 959	$ 1,097
Cost of service sales
Finite-Lived Intangible Assets [Line Items]
Amortization expense	373	399
General and administrative
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 586	$ 698