Goodwill and Intangible Assets - Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Intangible Assets [Line Items]
Accumulated amortization	$ (89,118)	$ (102,687)
Foreign currency exchange rate fluctuations	(1,174)	(1,122)
Total intangibles assets, gross carrying amount	224,393	247,495
Total intangible assets, net carrying amount	134,101	143,686
Customer relationships
Intangible Assets [Line Items]
Gross carrying amount	135,234	135,234
Accumulated amortization	(49,999)	(45,029)
Foreign currency exchange rate fluctuations	(1,215)	(1,185)
Total	$ 84,020	$ 89,020
Customer relationships | Minimum
Intangible Assets [Line Items]
Useful life (in years)	1 year	1 year
Customer relationships | Maximum
Intangible Assets [Line Items]
Useful life (in years)	30 years	30 years
Acquired technology
Intangible Assets [Line Items]
Gross carrying amount	$ 77,142	$ 78,122
Accumulated amortization	(32,230)	(29,206)
Foreign currency exchange rate fluctuations	25	42
Total	$ 44,937	$ 48,958
Acquired technology | Minimum
Intangible Assets [Line Items]
Useful life (in years)	3 years	3 years
Acquired technology | Maximum
Intangible Assets [Line Items]
Useful life (in years)	20 years	20 years
Backlog
Intangible Assets [Line Items]
Gross carrying amount	$ 1,150	$ 21,350
Accumulated amortization	(647)	(20,703)
Foreign currency exchange rate fluctuations	0	0
Total	$ 503	$ 647
Backlog | Minimum
Intangible Assets [Line Items]
Useful life (in years)	4 years	1 year
Backlog | Maximum
Intangible Assets [Line Items]
Useful life (in years)	4 years	4 years
Trade names
Intangible Assets [Line Items]
Gross carrying amount	$ 7,650	$ 7,650
Accumulated amortization	(4,699)	(4,361)
Foreign currency exchange rate fluctuations	14	17
Total	$ 2,965	$ 3,306
Trade names | Minimum
Intangible Assets [Line Items]
Useful life (in years)	1 year	1 year
Trade names | Maximum
Intangible Assets [Line Items]
Useful life (in years)	12 years	12 years
Patents
Intangible Assets [Line Items]
Gross carrying amount	$ 3,217	$ 3,239
Accumulated amortization	(1,543)	(1,488)
Foreign currency exchange rate fluctuations	2	4
Total	$ 1,676	$ 1,755
Patents | Minimum
Intangible Assets [Line Items]
Useful life (in years)	2 years	2 years
Patents | Maximum
Intangible Assets [Line Items]
Useful life (in years)	20 years	20 years
Non-compete agreements
Intangible Assets [Line Items]
Gross carrying amount		$ 1,900
Accumulated amortization		(1,900)
Foreign currency exchange rate fluctuations		0
Total		$ 0
Useful life (in years)	0 years	3 years