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]
Beginning balances (shares) at Sep. 30, 2018		41,939,403
Stock issued under employee incentive plans (shares)		20,463
Ending balances (shares) at Dec. 31, 2018		41,959,866
Beginning balances at Sep. 30, 2018	$ 674.5	$ 41.9	$ 506.3	$ 125.1	$ 1.2
Net income	3.9	0.0	0.0	3.3	0.6
Stock issued under employee incentive plans	0.1	0.1	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
Stock-based compensation expense	0.1	0.0	0.1	0.0	0.0
Distributions to noncontrolling interests	(0.5)	0.0	0.0	0.0	(0.5)
Ending balances at Dec. 31, 2018	678.0	$ 42.0	506.3	128.4	1.3
Beginning balances (shares) at Sep. 30, 2018		41,939,403
Ending balances (shares) at Jun. 30, 2019		41,959,866
Beginning balances at Sep. 30, 2018	674.5	$ 41.9	506.3	125.1	1.2
Net income	23.6
Ending balances at Jun. 30, 2019	695.3	$ 42.0	507.3	145.4	0.6
Beginning balances (shares) at Dec. 31, 2018		41,959,866
Ending balances (shares) at Mar. 31, 2019		41,959,866
Beginning balances at Dec. 31, 2018	678.0	$ 42.0	506.3	128.4	1.3
Net income	12.8	0.0	0.0	10.1	2.7
Stock-based compensation expense	0.1	0.0	0.1	0.0	0.0
Distributions to noncontrolling interests	(3.1)	0.0	0.0	0.0	(3.1)
Ending balances at Mar. 31, 2019	687.8	$ 42.0	506.4	138.5	0.9
Ending balances (shares) at Jun. 30, 2019		41,959,866
Net income	6.9	$ 0.0	0.0	6.9	0.0
Stock-based compensation expense	0.9	0.0	0.9	0.0	0.0
Distributions to noncontrolling interests	(0.3)	0.0	0.0	0.0	(0.3)
Ending balances at Jun. 30, 2019	695.3	$ 42.0	507.3	145.4	0.6
Beginning balances (shares) at Sep. 30, 2019		47,997,366
Stock issued under employee incentive plans (shares)		27,993
Ending balances (shares) at Dec. 31, 2019		48,025,359
Beginning balances at Sep. 30, 2019	808.9	$ 48.0	602.2	158.1	0.6
Net income	16.8	0.0	0.0	16.9	(0.1)
Stock issued under employee incentive plans	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
Stock-based compensation expense	0.5	0.0	0.5	0.0	0.0
Distributions to noncontrolling interests	(0.4)	0.0	0.0	0.0	(0.4)
Ending balances at Dec. 31, 2019	825.6	$ 48.0	602.5	175.0	0.1
Beginning balances (shares) at Sep. 30, 2019		47,997,366
Ending balances (shares) at Jun. 30, 2020		48,059,921
Beginning balances at Sep. 30, 2019	808.9	$ 48.0	602.2	158.1	0.6
Net income	37.2
Ending balances at Jun. 30, 2020	846.9	$ 48.1	603.5	194.7	0.6
Beginning balances (shares) at Dec. 31, 2019		48,025,359
Ending balances (shares) at Mar. 31, 2020		48,025,359
Beginning balances at Dec. 31, 2019	825.6	$ 48.0	602.5	175.0	0.1
Net income	10.4	0.0	0.0	9.6	0.8
Stock-based compensation expense	0.8	0.0	0.8	0.0	0.0
Ending balances at Mar. 31, 2020	836.8	$ 48.0	603.3	184.6	0.9
Stock issued under employee incentive plans (shares)		34,562
Ending balances (shares) at Jun. 30, 2020		48,059,921
Net income	10.1	$ 0.0	0.0	10.1	0.0
Stock issued under employee incentive plans	0.1	0.1	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
Stock-based compensation expense	0.3	0.0	0.3	0.0	0.0
Distributions to noncontrolling interests	(0.3)	0.0	0.0	0.0	(0.3)
Ending balances at Jun. 30, 2020	$ 846.9	$ 48.1	$ 603.5	$ 194.7	$ 0.6