Assets and Liabilities, at Fair Value - Available for Sale Securities in OCI (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Assets and Liabilities, at Fair Value [Abstract]
Equity Investments in Exchange Stock - Cost	$ 3.7	$ 3.7
Equity Investments in Exchange Stock - Fair Value	5.6	4.8
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	(3.3)
Deferred Tax Liabilities, Accumulated Other Comprehensive Income - AFS Securities	2.0
Proceeds from Shares of Exchanges Sold		1.5
Gain (Loss) on Sale of Exchange Shares		0.9
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	5.4	0.1	$ 8.3
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	$ 2.7	$ 0.2	$ 0.6