Goodwill - Changes in Carrying Amount of Goodwill (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Goodwill [Roll Forward]
Balance at December 31, 2018	$ 279,259
Goodwill acquired during the period	0
Adjustments to preliminary purchase price allocations	0
Foreign currency translation	3,758
Balance at June 30, 2019	283,017
Services
Goodwill [Roll Forward]
Balance at December 31, 2018	243,476
Goodwill acquired during the period	0
Adjustments to preliminary purchase price allocations	0
Foreign currency translation	3,963
Balance at June 30, 2019	247,439
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	(205)
Balance at June 30, 2019	35,578
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 June 30, 2019	$ 0