Derivative instruments (Tables)

9 Months Ended

Sep. 30, 2015

Derivative Instruments And Hedging Activities Disclosure [Abstract]

Schedule of Fair Values of Derivative Instruments

The tables below disclose the types of derivative instruments the Company owns, the classifications and fair values of these instruments within the balance sheet, and the amount of gain (loss) recognized in other comprehensive income (loss).

(U.S. Dollars, in thousands) As of September 30, 2015	Fairvalue: favorable (unfavorable)		Balance sheet location
Cross-currency swap	$	4,633	Other long-term assets
Warrants	$	311	Other long-term assets
As of December 31, 2014
Cross-currency swap	$	2,504	Other long-term assets
Warrants	$	321	Other long-term assets

Schedule of Gain (Loss) Recognized in Other Comprehensive Income (Loss)

	Three Months Ended September 30,					Nine Months Ended September 30,
(U.S. Dollars, in thousands)	2015			2014		2015		2014
Cross-currency swap unrealized gain (loss)    recorded in other comprehensive income    (loss), net of taxes	$	(706	)	$	112	$	230	$	184
Warrants unrealized gain recorded in other    comprehensive income (loss), net of taxes	$	—		$	—	$	—	$	—