Commitments and contingencies (Details) $ in Thousands	Sep. 30, 2015 USD ($)
Commitments and Contingencies Disclosure [Line Items]
2015	$ 23,388	[1]
2016	5,115
2017	2,839
2018	0
Thereafter	0
Total	31,342
Obligations for investment contracts [Member]
Commitments and Contingencies Disclosure [Line Items]
2015	0	[1],[2]
2016	3,256	[2]
2017	2,442	[2]
2018	0	[2]
Thereafter	0	[2]
Total	5,698	[2]
Obligations for purchasing and service agreements [Member]
Commitments and Contingencies Disclosure [Line Items]
2015	23,388	[1]
2016	1,859
2017	397
2018	0
Thereafter	0
Total	$ 25,644

[1] Remaining 3 months in 2015.

[2] Capital Commitment to the Venture Fund