Note 4 - Marketable Securities

6 Months Ended

Mar. 31, 2025

Notes to Financial Statements

Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]

4. Marketable Securities

The Company had sales and maturities of marketable securities of $59.0 million and $80.2 million in the three months ended March 31, 2025 and 2024, respectively. The Company had sales and maturities of marketable securities of $184.6 million and $190.5 million in the six months ended March 31, 2025 and 2024, respectively. There were immaterial realized gains or losses in each of the three and six months ended March 31, 2025 and 2024 on sales and maturities of marketable securities. 

The following is a summary of the amortized cost and the fair value, including accrued interest receivable as well as unrealized gains (losses) on the short-term and long-term marketable securities as of March 31, 2025 and  September 30, 2024 (in thousands):

			Gross			Gross
	Amortized		Unrealized			Unrealized
	Cost		Losses			Gains		Fair Value
March 31, 2025:
U.S. Treasury securities and obligations of U.S. government agencies	$	214,926	$	(99	)	$	132	$	214,959
Bank certificates of deposit		1,975		(2	)		—		1,973
Corporate securities		25,254		(31	)		—		25,223
Municipal securities		9,286		—			37		9,323
	$	251,441	$	(132	)	$	169	$	251,478
September 30, 2024:
U.S. Treasury securities and obligations of U.S. government agencies	$	118,159	$	(119	)	$	51	$	118,091
Bank certificates of deposit		5,212		(13	)		1		5,200
Corporate securities		77,580		(255	)		—		77,325
	$	200,951	$	(387	)	$	52	$	200,616

The amortized cost and fair value of the marketable securities by contractual maturities as of March 31, 2025 are presented below (in thousands):

	Amortized
	Cost		Fair Value
Due in one year or less	$	74,754	$	74,697
Due after one year through five years		173,099		173,193
Due after ten years		3,588		3,588
Total marketable securities	$	251,441	$	251,478

Expected maturities could differ from contractual maturities because the security issuers may have the right to prepay obligations without prepayment penalties.

Unrealized losses from fixed-income securities are primarily attributable to changes in interest rates. The Company does not believe any unrealized losses represent impairments based on the evaluation of the available evidence.