Share-based compensation (Tables)

12 Months Ended

Dec. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

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

The following tables present the detail of share-based compensation expense by line item in the consolidated statements of income as well as by award type, for the years ended December 31, 2021, 2020, and 2019:

	Year Ended December 31,
(U.S. Dollars, in thousands)	2021		2020		2019
Cost of sales	$	779	$	705	$	715
Sales and marketing		3,385		3,620		2,512
General and administrative		10,289		10,624		16,872
Research and development		979		1,258		1,441
Total	$	15,432	$	16,207	$	21,540

	Year Ended December 31,
(U.S. Dollars, in thousands)	2021		2020		2019
Stock options	$	1,893	$	2,571	$	4,054
Time-based restricted stock awards and stock units		7,437		8,485		11,084
Performance-based restricted stock awards and stock units		—		—		—
Market-based restricted stock units		4,414		3,509		4,733
Stock purchase plan		1,688		1,642		1,669
Total	$	15,432	$	16,207	$	21,540

Schedule of Assumptions Used in Determining Fair Value of Stock Options

The fair value of time-based stock options is determined using the Black-Scholes valuation model, with such value recognized as expense over the service period, which is typically four years, net of actual forfeitures. A summary of the Company’s assumptions used in determining the fair value of the stock options granted during the year is shown in the following table.

	Year Ended December 31,
	2021		2020		2019
Assumptions:
Expected term (in years)	6.0		5.5		5.0
Expected volatility	34.4% – 34.8%		30.2% – 35.1%		29.7% – 31.0%
Risk free interest rate	0.83% – 1.25%		0.28% – 1.65%		1.38% – 2.31%
Dividend yield		—		—		—
Weighted average grant date fair value	$	12.33	$	8.74	$	14.64

Schedule of Stock Option Plans

Summaries of the status of the Company’s stock option plans as of December 31, 2021, and 2020, and changes during the year ended December 31, 2021, are presented below:   

	Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term
Outstanding at December 31, 2020		1,491,019		$	39.56
Granted		72,995		$	35.59
Exercised		(89,151	)	$	36.68
Forfeited or expired		(77,809	)	$	45.49
Outstanding at December 31, 2021		1,397,054		$	39.20		5.04
Vested and expected to vest at December 31, 2021		1,397,054		$	39.20		5.04
Exercisable at December 31, 2021		944,630		$	41.10		3.51

Schedule of Changes in Time-Based and Market-Based Restricted Stock Awards and Stock Units

A summary of the status of our time-based and market-based restricted stock awards and stock units as of December 31, 2021, and 2020, and changes during the year ended December 31, 2021, are presented below:

	Time-based Restricted Stock Awards and Stock Units					Market-based Restricted Stock Units
	Shares			Weighted Average Grant Date Fair Value		Shares			Weighted Average Grant Date Fair Value
Outstanding at December 31, 2020		493,127		$	41.13		275,338		$	54.45
Granted		295,240		$	41.20		152,575		$	48.53
Vested and settled		(191,082	)	$	44.50		—		$	—
Cancelled		(37,917	)	$	41.00		(104,832	)	$	63.97
Outstanding at December 31, 2021		559,368		$	40.03		323,081		$	48.56