Note 3 - Stock-based Compensation (Tables)

12 Months Ended

Sep. 30, 2024

Notes Tables

Share-Based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity [Table Text Block]

				Weighted
				Average
				Grant Date
				Fair Value
	Units			Per Unit
Non-vested at September 30, 2023		348,353		$	71.76
Granted		111,510		$	74.23
Adjusted for performance		(13,749	)	$	69.73
Vested		(107,754	)	$	69.73
Forfeited		(49,155	)	$	75.55
Non-vested at September 30, 2024		289,205		$	73.36

				Weighted
				Average
				Grant Date
	Shares/			Fair Value
	Units			Per Share
Non-vested at September 30, 2023		122,989		$	65.85
Granted		60,210		$	59.92
Vested		(65,298	)	$	62.71
Forfeited		(32,342	)	$	65.70
Non-vested at September 30, 2024		85,559		$	64.13

Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	2024		2023		2022
Risk-free interest rate		4.66%		4.26%		0.79%
Expected dividend yield of stock		—		—		—
Expected volatility of stock		23.3%		33.8%		32.2%
Performance period (in years)		3.0		3.0		3.0

Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

	2024			2023			2022
Total compensation cost	$	6.6		$	11.2		$	7.5
Compensation cost capitalized		(0.8	)		(1.4	)		(1.1	)
Compensation cost recognized in net income		5.8			9.8			6.4
Income tax benefit recognized in net income		(1.3	)		(2.2	)		(1.5	)
Compensation cost recognized in net income, net of income tax	$	4.5		$	7.6		$	4.9