Patents and other intangible assets

12 Months Ended

Dec. 31, 2012

Goodwill And Intangible Assets Disclosure [Abstract]

Patents and other intangible assets

5. Patents and other intangible assets

	December 31,
(U.S. Dollars, in thousands)	2012			2011
	(Restated)			(Restated)
Cost
Patents	$	38,905		$	38,893
Trademarks—definite lived		657			545
		39,562			39,438
Accumulated amortization
Patents		(31,845	)		(30,211	)
Trademarks—definite lived		(427	)		(381	)
		(32,272	)		(30,592	)
Patents and other intangible assets, net	$	7,290		$	8,846

Amortization expense for intangible assets is estimated to be approximately $2.3 million, $1.6 million, $1.3 million, $1.2 million, $0.8 million and $0.1 million for the periods ending December 31, 2013, 2014, 2015, 2016, 2017 and 2018 and thereafter, respectively.