CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Noncontrolling Interest
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
Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture	0.0	0.0	0.0	0.0	0.0
Share-Based Payment Arrangement, Decrease for Tax Withholding Obligation	(0.1)	0.0	(0.1)	0.0	0.0
APIC, Share-Based Payment Arrangement, Increase for Cost Recognition	0.6	0.0	0.6	0.0	0.0
Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance 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	47.7
Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Mar. 31, 2023	1,248.8	49.9	642.3	555.6	1.0
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
Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture	0.1	0.1	0.0	0.0	0.0
Share-Based Payment Arrangement, Decrease for Tax Withholding Obligation	(0.7)	0.0	(0.7)	0.0	0.0
APIC, Share-Based Payment Arrangement, Increase for Cost Recognition	1.9	0.0	1.9	0.0	0.0
Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance 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
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Sep. 30, 2023	1,369.9	$ 49.9	644.2	674.8	1.0
Net income	38.2	0.0	0.0	38.2	0.0
Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture	0.0	0.0	0.0	0.0	0.0
Share-Based Payment Arrangement, Decrease for Tax Withholding Obligation	(0.2)	0.0	(0.2)	0.0	0.0
APIC, Share-Based Payment Arrangement, Increase for Cost Recognition	0.9	0.0	0.9	0.0	0.0
Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Dec. 31, 2023	1,408.8	$ 49.9	644.9	713.0	1.0
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture		6,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Sep. 30, 2023	1,369.9	$ 49.9	644.2	674.8	1.0
Net income	83.2
Stock Issued During Period, Value, New Issues	19.7
Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Mar. 31, 2024	1,472.9	50.6	663.3	758.0	1.0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2023	1,408.8	49.9	644.9	713.0	1.0
Net income	45.0	0.0	0.0	45.0	0.0
Stock Issued During Period, Value, New Issues	19.7	0.5	19.2	0.0	0.0
Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture	0.2	0.2	0.0	0.0	0.0
Share-Based Payment Arrangement, Decrease for Tax Withholding Obligation	(2.6)	0.0	(2.6)	0.0	0.0
APIC, Share-Based Payment Arrangement, Increase for Cost Recognition	1.8	0.0	1.8	0.0	0.0
Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Mar. 31, 2024	$ 1,472.9	$ 50.6	$ 663.3	$ 758.0	$ 1.0
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture		146,835