Goodwill - Changes in Carrying Amount of Goodwill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)
Goodwill [Roll Forward]
Balance at December 31, 2018	$ 279,259
Goodwill acquired during the period	1,753
Adjustments to preliminary purchase price allocations	923
Foreign currency translation	1,186
Balance at September 30, 2019	283,121
Services
Goodwill [Roll Forward]
Balance at December 31, 2018	243,476
Goodwill acquired during the period	1,753
Adjustments to preliminary purchase price allocations	923
Foreign currency translation	2,830
Balance at September 30, 2019	248,982
International
Goodwill [Roll Forward]
Balance at December 31, 2018	35,783
Goodwill acquired during the period	0
Adjustments to preliminary purchase price allocations	0
Foreign currency translation	(1,644)
Balance at September 30, 2019	34,139
Products and Systems
Goodwill [Roll Forward]
Balance at December 31, 2018	0
Goodwill acquired during the period	0
Adjustments to preliminary purchase price allocations	0
Foreign currency translation	0
Balance at September 30, 2019	$ 0