Assets and Liabilities, at Fair Value - Available for Sale Securities in OCI (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Assets and Liabilities, at Fair Value [Abstract]
Equity Investments in Exchange Stock - Cost	$ 3.7	$ 3.7
Equity Investments in Exchange Stock - Fair Value	6.4	5.6
Proceeds from Sale of Exchange Stock		2.1
Gain (Loss) on Disposition of Exchange Stock		1.2
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax - AFS securities		(3.3)
Deferred Tax Liabilities, Accumulated Other Comprehensive Income - AFS Securities		2.0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	0.0	5.4	$ 0.1
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	$ 0.0	$ 2.7	$ 0.2