Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis

Assets and liabilities measured at fair value on a recurring basis are categorized in the tables below based upon the lowest level of significant input to the valuations. Historically, we have presented short-term investments in the fair value table presented below. As our short-term investments in the accompanying consolidated balance sheets are comprised of U.S. Treasury Bills, these investments are classified as held-to-maturity investments and are not recorded at fair value on a recurring basis in our consolidated balance sheets. As such, we have removed short-term investments from the table below.



	December 31, 2018
	Level 1		Level 2		Level 3
Liabilities:
Contingent consideration ⁽¹⁾	$	—	$	—	$	5,531
Total	$	—	$	—	$	5,531

	December 31, 2017
	Level 1		Level 2		Level 3
Liabilities:
Contingent consideration ⁽¹⁾	$	—	$	—	$	412
Total	$	—	$	—	$	412

⁽¹⁾

Contingent consideration liability represents arrangements to pay the former owners of certain companies we acquired based on the former owners attaining future product release milestones. We use a probability-weighted discounted cash flow model to estimate the fair value of contingent consideration liabilities. These probability weightings are developed internally and assessed on a quarterly basis. For the year ended December 31, 2018, we paid $0.9 million as part of these arrangements. For the year ended December 31, 2017, we paid $0.5 million as part of these arrangements. The remaining change in the fair value of the contingent consideration from December 31, 2017 to December 31, 2018 was related to various business acquisitions we made during the year ended December 31, 2018, which included Laser Controls System, Lanmark and Opto-Tech SRL and its subsidiary Open Technologies SRL (collectively, “Open Technologies”), as well as changes in foreign currency exchange rates. The undiscounted maximum payment as of December 31, 2018 under the arrangements was $6.0 million, based on certain milestones.