Property, plant and equipment (Tables)

12 Months Ended

Dec. 31, 2016

Property Plant And Equipment [Abstract]

Schedule of Useful Lives of Assets

The useful lives of these assets are as follows:

	Years
Buildings	25 to 33
Plant and equipment	1 to 10
Instrumentation	3 to 4
Computer software	3 to 7
Furniture and fixtures	4 to 8

Schedule of Property Plant and Equipment

The assets and related accumulated depreciation are adjusted for property retirements and disposals, with the resulting gain or loss included in earnings. Fully depreciated assets remain in the accounts until retired from service.

	December 31,
(U.S. Dollars, in thousands)	2016			2015
Cost
Buildings	$	3,225		$	3,328
Plant and equipment		43,745			44,063
Instrumentation		71,962			62,282
Computer software		44,720			24,920
Furniture and fixtures		8,308			5,711
Construction in progress		1,907			19,101
		173,867			159,405
Accumulated depreciation		(124,951	)		(107,099	)
	$	48,916		$	52,306