Income Taxes - Reconciliation to effective income tax rate (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Income Tax Disclosure [Abstract]
Expected income tax expense at Federal statutory rate	$ 74.6	$ 41.4	$ 8.9
Valuation allowance for deferred tax assets	(47.4)	151.8	(139.6)
Preferred stock equity conversion feature	4.4	35.6	54.8
Residual tax on foreign earnings	90.9	(7.0)	29.8
Foreign rate differential	(23.1)	(18.8)	(14.1)
Provision-to-return	(7.7)	0	0
Gain on contingent purchase price reduction	0	0	(14.3)
Permanent items	6.5	5.7	9.5
Non-deductible stock based compensation	1.4	1.7	0
Exempt foreign income	(5.7)	(5.9)	(5.8)
Unrecognized tax benefits	2.2	4.1	(4.4)
State and local income taxes	0.8	(32.2)	(8.5)
Dividends received deduction	0	1.4	(0.9)
Inflationary adjustments	(0.5)	(0.2)	(0.8)
Capitalized transaction costs	1.0	5.6	0.3
Other	14.1	4.1	(0.2)
Reported income tax expense (benefit)	$ 111.5	$ 187.3	$ (85.3)
Effective tax rate	52.30%	158.30%	(335.90%)