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

	Three Months Ended March 31,
(U.S. Dollars, in thousands)	2019		2018
Cost of sales	$	187	$	125
Sales and marketing		610		449
General and administrative		4,564		3,045
Research and development		324		297
Total	$	5,685	$	3,916

	Three Months Ended March 31,
(U.S. Dollars, in thousands)	2019		2018
Stock options	$	2,112	$	622
Time-based restricted stock awards and units		1,706		1,447
Performance-based restricted stock awards and units		—		489
Market-based restricted stock units		1,347		953
Stock purchase plan		520		405
Total	$	5,685	$	3,916

During the three months ended March 31, 2019 and 2018, the Company issued 211,081 and 126,511 shares, respectively, of common stock related to stock purchase plan issuances, stock option exercises and the vesting of restricted stock awards and units.

During the first quarter of 2019, the Company entered into a Transition and Retirement Agreement (the “Retirement Agreement”) with the Company’s President and Chief Executive Officer. As part of the Retirement Agreement, certain time-based stock options and restricted stock awards were modified to accelerate the vesting to the retirement date. In addition, stock options were modified to extend the post-termination exercise period from 18 months under a standard qualified retirement to up to four years, dependent upon the remaining contractual term of the options. The Company recognized approximately $2.1 million in share-based compensation expense during the three months ended March 31, 2019, related to the Retirement Agreement which was charged to general and administrative expense in the condensed consolidated statements of operations and comprehensive income (loss).