Marketable Securities

9 Months Ended

Jun. 30, 2023

Investments, Debt and Equity Securities [Abstract]

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

3.    MARKETABLE SECURITIES

The Company’s portfolio of available-for-sale marketable securities consists of the following (in millions):    

	Current				Noncurrent
	June 30, 2023		September 30, 2022		June 30, 2023		September 30, 2022
U.S. Treasury and government securities	$	14.3	$	13.1	$	3.0	$	0.5
Corporate bonds and notes	—		0.2		—		—
Municipal bonds	0.6		7.0		—		—
Total marketable securities	$	14.9	$	20.3	$	3.0	$	0.5

Neither gross unrealized gains and losses nor realized gains and losses were material as of June 30, 2023, or September 30, 2022.