Credit Facilities and Indebtedness - Outstanding Debt (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Credit facilities	$ 525.0	$ 0
Total principal debt obligations	1,825.0	2,150.0
Swap fair value adjustments:
Total outstanding debt, net	1,878.6	2,192.9
Convertible Notes [Member]
3.25% Convertible Notes	0	850.0
Discounts:
Discounts	0	(23.3)
7.5% Bonds [Member]
Bonds	500.0	500.0
Discounts:
Discounts	(1.5)	(1.8)
Swap fair value adjustments:
Swap fair value adjustments	38.5	48.4
5.5% Bonds [Member]
Bonds	300.0	300.0
Discounts:
Discounts	(0.8)	(0.9)
Swap fair value adjustments:
Swap fair value adjustments	19.3	22.6
5.35% Bonds [Member]
Bonds	500.0	500.0
Discounts:
Discounts	$ (1.9)	$ (2.1)