Concentrations of risk and geographic information - Schedule of Revenue by Geographic Segment (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Revenue	$ 296,526	$ 220,755	$ 515,140	$ 404,291
Americas [Member]
Segment Reporting Information [Line Items]
Revenue	157,027	124,570	252,734	209,875
Europe, Middle East and Africa [Member]
Segment Reporting Information [Line Items]
Revenue	80,214	60,714	148,077	120,992
Asia and Pacific Area Countries [Member]
Segment Reporting Information [Line Items]
Revenue	$ 59,285	$ 35,471	$ 114,329	$ 73,424

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration