Restructuring and integration expense (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) Employees	Jun. 30, 2018 USD ($) Employees	Jun. 30, 2019 USD ($) Employees	Jun. 30, 2018 USD ($) Employees	Dec. 31, 2018 USD ($)
Restructuring and integration expense [Line Items]
Restructuring and integration expense	$ 17,497	$ 6,371	$ 23,780	$ 8,693
Number of employees in severance accruals | Employees	40	80	90	105
Other disclosures
Restructuring accruals	$ 4,285		$ 4,285		$ 3,461
Number of employees that have not started to receive severance benefits | Employees	20		20
Accrued liabilities [Member]
Other disclosures
Restructuring accruals					3,320
Other non-current liabilities [Member]
Other disclosures
Restructuring accruals					$ 141
Total cost of revenue [Member]
Restructuring and integration expense [Line Items]
Restructuring and integration expense	$ 155	$ 736	$ 946	$ 913
Operating expenses [Member]
Restructuring and integration expense [Line Items]
Restructuring and integration expense	17,342	5,635	22,834	7,780
Severance [Member]
Restructuring and integration expense [Line Items]
Restructuring and integration expense	2,913	3,804	5,146	4,648
Reversals	(216)	(95)	(385)	(230)
Net accruals	2,697	3,709	4,761	4,418
Other costs [Member]
Restructuring and integration expense [Line Items]
Restructuring and integration expense	$ 14,800	$ 2,662	$ 19,019	$ 4,275