Goodwill And Intangible Assets - Components of Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Sep. 30, 2016	Jun. 30, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill (not subject to amortization)	$ 2,002,046	$ 1,978,981	$ 1,978,894
Intangible assets:
Customer relationships and noncompete agreements	536,894	520,180	529,739
Accumulated amortization	(220,100)	(191,805)	(192,210)
Intangible assets, net (definite-lived)	316,794	328,375	337,529
Trademarks and tradenames (indefinite-lived)	82,944	82,944	82,944
Total intangible assets, net	$ 399,738	$ 411,319	$ 420,473