Goodwill and Intangible Assets - Components of Company's Goodwill and Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill (not subject to amortization)	$ 2,965.1	$ 2,953.4	$ 2,806.8	[1]
Intangible assets:
Customer relationships, noncompete agreements and other	764.6	761.1	709.3
Accumulated amortization	(292.2)	(282.4)	(271.9)
Intangible assets, net (definite-lived)	472.4	478.7	437.4
Trademarks and tradenames (indefinite-lived)	130.0	131.4	126.3
Total intangible assets, net	$ 602.4	$ 610.1	$ 563.7

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