CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Noncontrolling Interest
Common Stock, Shares, Outstanding		49,580,389
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Sep. 30, 2021	$ 1,015.9	$ 49.6	$ 636.2	$ 329.1	$ 1.0
Net income	40.5	0.0	0.0	40.5	0.0
Issuance of common stock (84,547 shares)	1.7	0.1	1.6	0.0	0.0
Issuances of common stock, Value	0.0	0.0	0.0	0.0	0.0
Stock-based compensation expense	0.4	0.0	0.4	0.0	0.0
Cash paid for shares withheld for taxes	(0.1)	0.0	(0.1)	0.0	0.0
Ending Balances at Dec. 31, 2021	1,058.4	$ 49.7	638.1	369.6	1.0
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture		10,832
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Sep. 30, 2021	1,015.9	$ 49.6	636.2	329.1	1.0
Net income	128.0
Ending Balances at Jun. 30, 2022	1,147.9	$ 49.8	640.0	457.1	1.0
Common Stock, Shares, Outstanding		49,675,768
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2021	1,058.4	$ 49.7	638.1	369.6	1.0
Net income	47.8	0.0	0.0	47.8	0.0
Issuances of common stock, Value	0.0	0.0	0.0	0.0	0.0
Stock-based compensation expense	1.6	0.0	1.6	0.0	0.0
Cash paid for shares withheld for taxes	(0.4)	0.0	(0.4)	0.0	0.0
Ending Balances at Mar. 31, 2022	1,107.4	$ 49.7	639.3	417.4	1.0
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture		62,576
Common Stock, Shares, Outstanding		49,738,344
Net income	39.7	$ 0.0	0.0	39.7	0.0
Issuances of common stock, Value	0.1	0.1	0.0	0.0	0.0
Stock-based compensation expense	0.8	0.0	0.8	0.0	0.0
Cash paid for shares withheld for taxes	(0.1)	0.0	(0.1)	0.0	0.0
Ending Balances at Jun. 30, 2022	1,147.9	$ 49.8	640.0	457.1	1.0
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture		21,136
Common Stock, Shares, Outstanding		49,759,480
Common Stock, Shares, Outstanding		49,761,480
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Sep. 30, 2022	1,199.3	$ 49.8	640.6	507.9	1.0
Net income	20.8	0.0	0.0	20.8	0.0
Issuances of common stock, Value	0.0	0.0	0.0	0.0	0.0
Stock-based compensation expense	0.6	0.0	0.6	0.0	0.0
Cash paid for shares withheld for taxes	(0.1)	0.0	(0.1)	0.0	0.0
Ending Balances at Dec. 31, 2022	1,220.6	$ 49.8	641.1	528.7	1.0
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture		11,075
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Sep. 30, 2022	1,199.3	$ 49.8	640.6	507.9	1.0
Net income	94.5
Ending Balances at Jun. 30, 2023	1,296.5	$ 49.9	643.2	602.4	1.0
Common Stock, Shares, Outstanding		49,772,555
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2022	1,220.6	$ 49.8	641.1	528.7	1.0
Net income	26.9	0.0	0.0	26.9	0.0
Issuances of common stock, Value	0.1	0.1	0.0	0.0	0.0
Stock-based compensation expense	1.9	0.0	1.9	0.0	0.0
Cash paid for shares withheld for taxes	(0.7)	0.0	(0.7)	0.0	0.0
Ending Balances at Mar. 31, 2023	1,248.8	$ 49.9	642.3	555.6	1.0
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture		125,154
Common Stock, Shares, Outstanding		49,897,709
Net income	46.8	$ 0.0	0.0	46.8	0.0
Issuances of common stock, Value	0.0	0.0	0.0	0.0	0.0
Stock-based compensation expense	0.9	0.0	0.9	0.0	0.0
Ending Balances at Jun. 30, 2023	$ 1,296.5	$ 49.9	$ 643.2	$ 602.4	$ 1.0
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture		6,004
Common Stock, Shares, Outstanding		49,903,713