Revenue recognition (Tables)

9 Months Ended

Sep. 30, 2017

Revenue Recognition [Abstract]

Schedule of Net Sales

The table below presents net sales, which includes product sales and marketing service fees, for both the three and nine months ended September 30, 2017 and 2016.

	Three Months Ended September 30,				Nine Months Ended September 30,
(U.S. Dollars, in thousands)	2017		2016		2017		2016
Product sales	$	90,645	$	84,997	$	272,954	$	261,490
Marketing service fees		14,602		13,500		43,973		39,761
Net sales	$	105,247	$	98,497	$	316,927	$	301,251