Acquisitions - Intangible assets purchase transaction (Details) - Zappa Stewart $ in Thousands	1 Months Ended
	Dec. 31, 2017 USD ($)
Identifiable intangible assets purchased
Intangible assets	$ 30,240
Customer Relationships
Identifiable intangible assets purchased
Intangible assets	$ 28,500
Useful life	7 years 10 months 24 days
Technology
Identifiable intangible assets purchased
Intangible assets	$ 900
Useful life	7 years
Trade names
Identifiable intangible assets purchased
Intangible assets	$ 840
Useful life	4 years