Goodwill and Intangible Assets - Intangible Assets, Net (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Intangible Assets [Line Items]
Accumulated amortization	$ (96,673)	$ (78,872)
Foreign currency exchange rate fluctuations	(854)	(516)
Total intangibles assets, gross carrying amount	247,495	247,495
Total intangible assets, net carrying amount	149,968	168,107
In-process technology
Intangible Assets [Line Items]
Indefinite-lived intangible assets	3,900	3,900
Customer relationships
Intangible Assets [Line Items]
Gross carrying amount	135,234	135,234
Accumulated amortization	(42,435)	(33,988)
Foreign currency exchange rate fluctuations	(1,003)	(787)
Net carrying amount	$ 91,796	$ 100,459
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	$ 74,222	$ 74,222
Accumulated amortization	(27,011)	(21,345)
Foreign currency exchange rate fluctuations	123	221
Net carrying amount	$ 47,334	$ 53,098
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	$ 21,350	$ 21,350
Accumulated amortization	(19,823)	(17,182)
Foreign currency exchange rate fluctuations	0	0
Net carrying amount	$ 1,527	$ 4,168
Backlog | Minimum
Intangible Assets [Line Items]
Useful life (in years)	1 year	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	(4,193)	(3,688)
Foreign currency exchange rate fluctuations	21	40
Net carrying amount	$ 3,478	$ 4,002
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	$ 3,239	$ 3,239
Accumulated amortization	(1,461)	(1,369)
Foreign currency exchange rate fluctuations	5	10
Net carrying amount	$ 1,783	$ 1,880
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	$ 1,900
Accumulated amortization	(1,750)	(1,300)
Foreign currency exchange rate fluctuations	0	0
Net carrying amount	$ 150	$ 600
Useful life (in years)	3 years	3 years