Goodwill and Intangible Assets - Components of Company's Goodwill and Intangible Assets (Details) - USD ($) $ in Millions	Jun. 30, 2015	Sep. 30, 2014	Jun. 30, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill (not subject to amortization)	$ 2,927.7	$ 2,833.4	$ 2,885.1
Intangible assets:
Customer relationships, noncompete agreements and other	761.9	712.0	717.3
Accumulated amortization	(268.4)	(263.8)	(259.0)
Intangible assets, net (definite-lived)	493.5	448.2	458.3
Trademarks and tradenames (indefinite-lived)	135.0	128.2	132.0
Total intangible assets, net	$ 628.5	$ 576.4	$ 590.3