Share-based compensation (Tables)

6 Months Ended

Jun. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Share-Based Compensation by Line Item in Condensed Consolidated Statements of Income

The following tables present the detail of share-based compensation by line item in the condensed consolidated statements of income as well as by award type:

	Three Months Ended June 30,				Six Months Ended June 30,
(U.S. Dollars, in thousands)	2018		2017		2018		2017
Cost of sales	$	132	$	137	$	257	$	286
Sales and marketing		473		319		922		679
General and administrative		4,249		2,005		7,294		4,107
Research and development		361		215		658		420
	$	5,215	$	2,676	$	9,131	$	5,492

	Three Months Ended June 30,				Six Months Ended June 30,
(U.S. Dollars, in thousands)	2018		2017		2018		2017
Stock options	$	1,241	$	523	$	1,863	$	1,118
Time-based restricted stock awards and units		1,789		1,239		3,236		2,531
Performance-based restricted stock awards		270		113		759		225
Performance-based and market-based restricted stock units		1,604		472		2,557		938
Stock purchase plan		311		329		716		680
	$	5,215	$	2,676	$	9,131	$	5,492