Note 4 — Investments

At December 31, 2018 and 2017 the amortized cost and fair value of marketable securities were as follows:


			Gross		Gross
	Amortized		Unrealized		Unrealized		Estimated
	Cost		Gains		Losses		Fair Value
	(in thousands)
December 31, 2018
U.S. treasuries	$	37,191	$	—	$	(7)	$	37,184
Corporate debt		8,525		—		(9)		8,516
Commercial paper		2,489		—		—		2,489
Total	$	48,205	$	—	$	(16)	$	48,189

December 31, 2017
U.S. treasuries	$	33,914	$	—	$	(19)	$	33,895
Corporate debt		10,894		—		(8)		10,886
Commercial paper		2,999		—		—		2,999
Total	$	47,807	$	—	$	(27)	$	47,780

Available-for-sale securities in a loss position at December 31, 2018 and 2017 were as follows:


	December 31, 2018				December 31, 2017
			Gross				Gross
	Estimated		Unrealized		Estimated		Unrealized
	Fair Value		Losses		Fair Value		Losses
	(in thousands)
U.S. treasuries	$	37,184	$	(7)	$	33,895	$	(19)
Corporate debt		8,516		(9)		10,886		(8)
Total	$	45,700	$	(16)	$	44,781	$	(27)

At December 31, 2018 and 2017, there were no short-term investments that had been in a continuous loss position for more than 12 months.

The maturities of securities classified as available-for-sale at December 31, 2018 were all due in one year or less. Actual maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. The realized gains or losses for the years ended December 31, 2018, 2017, and 2016 were immaterial.

Other Investments

Veeco has an ownership interest of less than 20% in a non-marketable investment, Kateeva, Inc. (“Kateeva”), over which Veeco does not exert significant influence. The carrying value of the investment was $21.0 million at December 31, 2018 and 2017. Additionally, during the year ended December 31, 2018, the Company made a separate non-marketable investment of $3.5 million in another entity. The Company does not exert significant influence over this investment and its ownership interest is less than 20%. Neither equity investment has a readily observable market price, and therefore the Company has elected to measure these investments at cost, adjusted for changes in observable market prices minus impairment. The investments are included in “Other assets” on the Consolidated Balance Sheets. There were no changes in observable market prices for either investment for the year ended December 31, 2018. These investments are subject to periodic impairment reviews; as there are no open-market valuations, the impairment analyses require judgment. The analyses include assessments of the companies’ financial condition, the business outlooks for their products and technologies, their projected results and cash flow, business valuation indications from recent rounds of financing, the likelihood of obtaining subsequent rounds of financing, and the impact of equity preferences held by Veeco relative to other investors. There were no impairment charges recorded for either investment for the years ended December 31, 2018, 2017, or 2016.