Consolidated Statements of Total Equity (Unaudited) Statement - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Noncontrolling Interest [Member]
Common Stock, Shares, Outstanding		48,061,921
Beginning balances at Sep. 30, 2020	$ 871.8	$ 48.1	$ 603.9	$ 218.9	$ 0.9
Net income	22.1	0.0	0.0	22.0	0.1
Stock issued under employee incentive plans	0.0	0.0	0.0	0.0	0.0
Cash paid for shares withheld for taxes	(0.1)	0.0	0.1	0.0	0.0
Stock-based compensation expense	0.3	0.0	0.3	0.0	0.0
Ending balances at Dec. 31, 2020	894.1	$ 48.1	604.1	240.9	1.0
Stock issued under employee incentive plans (shares)		14,722
Beginning balances at Sep. 30, 2020	871.8	$ 48.1	603.9	218.9	0.9
Net income	66.4
Ending balances at Jun. 30, 2021	970.4	$ 49.5	634.9	285.1	0.9
Common Stock, Shares, Outstanding		48,076,643
Beginning balances at Dec. 31, 2020	894.1	$ 48.1	604.1	240.9	1.0
Net income	28.4	0.0	0.0	28.4	0.0
Issuance of common stock	$ 23.3	1.0	22.3	0.0	0.0
Stock Issued During Period, Shares, New Issues	1,018,503
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	$ 1.9	0.0	(1.7)	0.0	(0.2)
Stock issued under employee incentive plans	0.0	0.0	0.0	0.0	0.0
Cash paid for shares withheld for taxes	(0.3)	0.0	0.3	0.0	0.0
Stock-based compensation expense	0.9	0.0	0.9	0.0	0.0
Ending balances at Mar. 31, 2021	$ 944.5	$ 49.1	625.3	269.3	0.8
Stock issued under employee incentive plans (shares)		29,655
Common Stock, Shares, Outstanding	49,124,801
Net income	$ 15.9	$ 0.0	0.0	15.8	0.1
Issuance of common stock	$ 9.3	0.4	8.9	0.0	0.0
Stock Issued During Period, Shares, New Issues	378,736
Stock issued under employee incentive plans	$ 0.0	0.0	0.0	0.0	0.0
Cash paid for shares withheld for taxes	(0.1)	0.0	0.1	0.0	0.0
Stock-based compensation expense	0.8	0.0	0.8	0.0	0.0
Ending balances at Jun. 30, 2021	$ 970.4	$ 49.5	634.9	285.1	0.9
Stock issued under employee incentive plans (shares)		23,571
Common Stock, Shares, Outstanding	49,527,108
Common Stock, Shares, Outstanding	49,580,389
Beginning balances 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	1.7	$ 0.1	1.6	0.0	0.0
Stock Issued During Period, Shares, New Issues		84,547
Stock issued under employee incentive plans	0.0	$ 0.0	0.0	0.0	0.0
Cash paid for shares withheld for taxes	(0.1)	0.0	0.1	0.0	0.0
Stock-based compensation expense	0.4	0.0	0.4	0.0	0.0
Ending balances at Dec. 31, 2021	1,058.4	$ 49.7	638.1	369.6	1.0
Stock issued under employee incentive plans (shares)		10,832
Beginning balances 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
Beginning balances 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
Stock Issued During Period, Shares, New Issues		62,576
Stock issued under employee incentive plans	0.0	$ 0.0	0.0	0.0	0.0
Cash paid for shares withheld for taxes	(0.4)	0.0	0.4	0.0	0.0
Stock-based compensation expense	1.6	0.0	1.6	0.0	0.0
Ending balances at Mar. 31, 2022	1,107.4	$ 49.7	639.3	417.4	1.0
Common Stock, Shares, Outstanding		49,738,344
Net income	39.7	$ 0.0	0.0	39.7	0.0
Stock Issued During Period, Shares, New Issues		21,136
Stock issued under employee incentive plans	0.1	$ 0.1	0.0	0.0	0.0
Cash paid for shares withheld for taxes	(0.1)	0.0	0.1	0.0	0.0
Stock-based compensation expense	0.8	0.0	0.8	0.0	0.0
Ending balances at Jun. 30, 2022	$ 1,147.9	$ 49.8	$ 640.0	$ 457.1	$ 1.0
Common Stock, Shares, Outstanding		49,759,480