Property, plant and equipment (Tables)

12 Months Ended

Dec. 31, 2020

Property Plant And Equipment [Abstract]

Schedule of Useful Lives of Assets

The useful lives of these assets are generally 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)	2020			2019
Cost
Buildings	$	4,096		$	3,731
Plant and equipment		50,159			46,470
Instrumentation		93,252			82,327
Computer software		52,565			49,696
Furniture and fixtures		8,024			7,328
Construction in progress		1,628			2,201
Finance lease assets		23,337			21,179
Property, plant, and equipment, gross		233,061			212,932
Accumulated depreciation		(169,448	)		(150,205	)
Property, plant, and equipment, net	$	63,613		$	62,727