Summary of significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2014

Accounting Policies [Abstract]

Schedule of Useful Lives

The useful lives are as follows:

	Years
Buildings	25 to 33
Plant equipment and instrumentation	2 to 10
Furniture and fixtures	4 to 8

Components of Changes in Accumulated Other Comprehensive Income (Loss)

The components of and changes in accumulated other comprehensive income (loss) are as follows:

(U.S. Dollars in thousands)	ForeignCurrency Translation Adjustments			Change in Fair Value			Accumulated Other Comprehensive (Loss) Income
Balance at December 31, 2012 (Restated)		5,359			131			5,490
Unrealized loss on derivative instruments, net of tax    benefit of $164		—			(279	)		(279	)
Foreign currency translation adjustment (1)		(1,708	)		—			(1,708	)
Balance at December 31, 2013 (Restated)	$	3,651		$	(148	)	$	3,503
Unrealized gain on cross-currency swaps, net of tax    expense of $59		—			248			248
Foreign currency translation adjustment (1)		(4,133	)		—			(4,133	)
Balance at December 31, 2014	$	(482	)	$	100		$	(382	)

(1) As the cash generally remains indefinitely reinvested in the non U.S. dollar denominated foreign subsidiaries, no deferred taxes are recognized on the related foreign currency translation adjustment.