Income taxes: Components of (loss) income before income taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Components of income before income taxes
Domestic	$ 24,849	$ (4,084)	$ 54,179	$ 27,818
Foreign	(2,825)	(2,471)	(8,024)	(10,242)
Income (loss) before income taxes	$ 22,024	$ (6,555)	$ 46,155	$ 17,576