Note 5 - Marketable Securities

12 Months Ended

Sep. 30, 2024

Notes to Financial Statements

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

5.    Marketable Securities

During fiscal years 2024 and 2023, the Company had sales and maturities of marketable securities of $0.7 billion and $1.1 billion, respectively. Realized gains on the sales of marketable securities were insignificant for the fiscal year ended September 30, 2024 and realized losses on the sales of marketable securities were $0.8 million for the fiscal year ended September 30, 2023.

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 September 30, 2024 and 2023 (in thousands):

			Gross			Gross
	Amortized		Unrealized			Unrealized
	Cost		Losses			Gains		Fair Value
September 30, 2024:
U.S. Treasury securities and obligations of U.S. government agencies	$	118,159	$	(119	)	$	51	$	118,091
Bank certificates of deposits		5,212		(13	)		1		5,200
Corporate securities		77,580		(255	)		—		77,325
	$	200,951	$	(387	)	$	52	$	200,616
September 30, 2023:
U.S. Treasury securities and obligations of U.S. government agencies	$	227,804	$	(2,573	)	$	—	$	225,231
Bank certificates of deposits		8,122		(170	)		—		7,952
Corporate securities		221,155		(4,127	)		—		217,028
	$	457,081	$	(6,870	)	$	—	$	450,211

The fair values of the marketable securities by contractual maturities at September 30, 2024 are presented below (in thousands).

	Amortized
	Cost		Fair Value
Due in one year or less	$	151,510	$	151,162
Due after one year through five years		45,654		45,667
Due after five years through ten years		—		—
Due after ten years		3,787		3,787
Total marketable securities	$	200,951	$	200,616

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.