Note 4 - Marketable Securities

9 Months Ended

Jun. 30, 2024

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 $241.0 million and $223.3 million in the three months ended June 30, 2024 and 2023, respectively. The Company had sales and maturities of marketable securities of $431.5 million and $951.5 million in the nine months ended June 30, 2024 and 2023, respectively. There were insignificant realized gains or losses in each of the three months ended  June 30, 2024 and 2023 on the sale and maturity of marketable securities. There were insignificant and $0.8 million realized losses in the nine months ended June 30, 2024 and 2023, respectively, on the sale and maturity 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 June 30, 2024 and  September 30, 2023 (in thousands):

			Gross			Gross
	Amortized		Unrealized			Unrealized
	Cost		Losses			Gains		Fair Value
June 30, 2024:
U.S. Treasury securities and obligations of U.S. government agencies	$	298,843	$	(786	)	$	—	$	298,057
Bank certificates of deposit		5,422		(44	)		—		5,378
Corporate securities		103,869		(941	)		—		102,928
Municipal securities		1,019		—			—		1,019
	$	409,153	$	(1,771	)	$	—	$	407,382
September 30, 2023:
U.S. Treasury securities and obligations of U.S. government agencies	$	227,804	$	(2,573	)	$	—	$	225,231
Bank certificates of deposit		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 as of June 30, 2024 were as follows (in thousands):

	Amortized
	Cost		Fair Value
Due in one year or less	$	260,690	$	259,296
Due after one year through five years		144,955		144,578
Due after five years through ten years		—		—
Due after ten years		3,508		3,508
Total marketable securities	$	409,153	$	407,382

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 its evaluation of the available evidence.