Goodwill and Intangible Assets - Schedule of Changes in Carrying Amount of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Line Items]
Goodwill			$ 1,898,586
Accumulated goodwill impairment losses			(200,631)
Goodwill
Beginning Balance	$ 1,779,745	$ 1,697,955
Foreign currency translation	52,548	(4,149)
Acquisitions	61,483	85,939
Acquisition adjustments	1,798
Ending Balance	1,895,574	1,779,745
FMT
Goodwill and Intangible Assets Disclosure [Line Items]
Goodwill			601,762
Accumulated goodwill impairment losses			(20,721)
Goodwill
Beginning Balance	578,925	581,041
Foreign currency translation	10,365	(2,116)
Acquisitions	60,431	0
Acquisition adjustments	0
Ending Balance	649,721	578,925
HST
Goodwill and Intangible Assets Disclosure [Line Items]
Goodwill			895,177
Accumulated goodwill impairment losses			(149,820)
Goodwill
Beginning Balance	831,772	745,357
Foreign currency translation	29,058	476
Acquisitions	0	85,939
Acquisition adjustments	1,798
Ending Balance	862,628	831,772
FSDP
Goodwill and Intangible Assets Disclosure [Line Items]
Goodwill			401,647
Accumulated goodwill impairment losses			$ (30,090)
Goodwill
Beginning Balance	369,048	371,557
Foreign currency translation	13,125	(2,509)
Acquisitions	1,052	0
Acquisition adjustments	0
Ending Balance	$ 383,225	$ 369,048