Goodwill and Intangible Assets - Components of Company's Goodwill and Intangible Assets (Details) - USD ($) $ in Millions	Jun. 30, 2016	Sep. 30, 2015	Jun. 30, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill (not subject to amortization)	$ 2,981.3	$ 2,953.4	$ 2,927.7	[1]
Intangible assets:
Customer relationships, noncompete agreements and other	778.1	761.1	761.9
Accumulated amortization	(321.3)	(282.4)	(268.4)
Intangible assets, net (definite-lived)	456.8	478.7	493.5
Trademarks and tradenames (indefinite-lived)	131.1	131.4	135.0
Total intangible assets, net	$ 587.9	$ 610.1	$ 628.5

[1] Certain amounts have been restated to reflect the current-year changes in our segment presentation as described above.