Commitments, guarantees and contingencies (Aggregate Minimum Rental Commitments Under Operating Leases) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]  
2015 $ 2,416
2016 1,848
2017 1,515
2018 1,309
2019 1,076
Thereafter 5,712
Operating Leases Total $ 13,876