Revenue recognition and accounts receivable (Tables)

12 Months Ended

Dec. 31, 2016

Revenue Recognition And Accounts Receivable [Abstract]

Schedule of Net Sales

The table below presents net sales, which includes product sales and marketing service fees, for each of the years ended December 31, 2016, 2015, and 2014.

	For the year ended December 31,
(U.S. Dollars, in thousands)	2016		2015		2014
Product sales	$	355,652	$	341,084	$	351,525
Marketing service fees		54,136		55,405		50,752
Net sales	$	409,788	$	396,489	$	402,277