Income taxes (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross balance at January 1	$ 50	$ 50
Additions based on tax positions related to the current year	0	0
Additions for tax positions of prior years	0	0
Reductions for tax positions of prior years	0	0
Settlements	(9)	0
Reductions due to lapse of applicable statute of limitations	0	0
Gross balance at December 31	41	50
Interest and penalties	22	22
Balance including interest and penalties at December 31	$ 63	$ 72