Share-based compensation (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

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

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

	Three Months Ended March 31,
(U.S. Dollars, in thousands)	2018		2017
Cost of sales	$	125	$	149
Sales and marketing		449		360
General and administrative		3,045		2,102
Research and development		297		205
	$	3,916	$	2,816

	Three Months Ended March 31,
(U.S. Dollars, in thousands)	2018		2017
Stock options	$	622	$	595
Time-based restricted stock awards		1,447		1,292
Performance-based restricted stock awards		489		112
Performance-based and market-based restricted stock units		953		466
Stock purchase plan		405		351
	$	3,916	$	2,816