Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent				0.60%
Deferred Tax Assets, Valuation Allowance	$ 4.5			$ 4.5			$ 4.0	$ 3.6
Income (Loss) from Continuing Operations before Income Taxes, Domestic							$ (24.7)	$ (9.7)	$ 16.5
Deferred Tax Liabilities, Net	3.3			3.3
Deferred Tax Liabilities, Unrealized Gains on Trading Securities	2.2			2.2
Income Tax Expense (Benefit)	$ 6.8		$ 3.3	$ 32.3	$ 5.4
Effective Income Tax Rate Reconciliation, Percent	23.00%			67.00%	24.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	$ 0.8			$ 20.1
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent	2.80%			42.00%
Deferred Income Tax Expense (Benefit)	$ 0.1	$ 8.9		$ 8.8
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount	$ 0.7	$ 12.0		$ 11.3
Scenario, Plan [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate						24.50%