Income taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current Income Tax Expense (Benefit) [Abstract]
Federal	$ 0	$ 0	$ 0
State and local	(107)	29	(236)
Foreign	(252)	(262)	(154)
Total current income tax (expense)/benefit	(359)	(233)	(390)
Deferred Income Tax Expense (Benefit) [Abstract]
Federal	(1,061)	(1,149)	(1,133)
State and local	(182)	(198)	(194)
Total deferred income tax (expense)	(1,243)	(1,347)	(1,327)
Income tax provision	$ (1,602)	$ (1,580)	$ (1,717)