CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Statement [Abstract]
Revenues	$ 318.4	$ 368.9	$ 958.0	$ 887.1
Cost of sales	246.9	283.9	730.6	698.7
Selling, general and administrative expense	29.3	26.4	86.5	71.3
Gain on sale of assets	(5.0)	0.0	(5.0)	(1.6)
Interest and other income	(4.4)	(3.8)	(15.7)	(7.5)
Income before income taxes	51.6	62.4	161.6	126.2
Income tax expense	12.9	15.6	39.8	31.7
Net income	$ 38.7	$ 46.8	$ 121.8	$ 94.5
Basic net income per common share	$ 0.76	$ 0.94	$ 2.42	$ 1.89
Weighted average number of common shares	50,755,276	50,056,126	50,322,916	49,963,326
Diluted net income per common share	$ 0.76	$ 0.93	$ 2.40	$ 1.89
Adjusted weighted average number of common shares	51,055,053	50,175,794	50,714,698	50,028,451