Goodwill and Intangible Assets - Schedule of Changes in Carrying Amount of Goodwill (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Goodwill [Roll Forward]
Balance at December 31, 2018	$ 1,697,955
Foreign currency translation	(3,735)
Acquisition adjustments	188
Balance at March 31, 2019	1,694,408
FMT
Goodwill [Roll Forward]
Balance at December 31, 2018	581,041
Foreign currency translation	(1,796)
Acquisition adjustments	0
Balance at March 31, 2019	579,245
HST
Goodwill [Roll Forward]
Balance at December 31, 2018	745,357
Foreign currency translation	(49)
Acquisition adjustments	188
Balance at March 31, 2019	745,496
FSDP
Goodwill [Roll Forward]
Balance at December 31, 2018	371,557
Foreign currency translation	(1,890)
Acquisition adjustments	0
Balance at March 31, 2019	$ 369,667