6. Shareholders' equity (Details) - Changes in Shareholders' Equity (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Changes in Shareholders' Equity [Abstract]
Balance at December 31, 2012			$ 33,369
Balance at September 30, 2013	31,409		31,409
Net income	1,451	23	3,826	1,739
Proceeds from issuance of shares from exercise of stock options			609	145
Share-based compensation expense			397	402
Incremental tax benefits from stock options exercised			113
Issuance of deferred stock units, net of relinquishments			111
Foreign currency translation adjustment			(11)
Reversal of deferred tax asset in connection with stock options forfeited			(73)
Dividends declared and paid on common stock			(1,738)
Purchases of common stock for treasury			$ (5,194)	$ (5,563)