Intangible assets: (Tables)

12 Months Ended

Dec. 31, 2012

Intangible assets:

Schedule of intangible assets

December 31, 2012	Cost		Accumulated amortization		Net book value
Patents and trademarks	$	20,192	$	1,758	$	18,434
Technology	6,961		1,901		5,060
Customer contracts	14,404		2,709		11,695
Non-compete agreement	44		18		26
	$	41,601	$	6,386	$	35,215

December 31, 2011	Cost		Accumulated amortization		Net book value
Patents and trademarks	$	19,508	$	727	$	18,781
Technology	6,380		1,122		5,258
Customer contracts	13,334		815		12,519
Non-compete agreement	37		13		24
	$	39,259	$	2,677	$	36,582