6. Shareholders' equity (Details) - Changes in Shareholders' Equity (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Changes in Shareholders' Equity [Abstract]
Balance at December 31, 2013			$ 32,521
Net income	175	1,215	569	2,375
Share-based compensation expense			309	276
Issuance of deferred stock units, net of relinquishments			56	446
Foreign currency translation adjustment			5
Dividends declared and paid on common stock			(1,248)
Balance at June 30, 2014	$ 32,212		$ 32,212