Intangible Assets, Goodwill and Acquisitions - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 855,930	$ 831,415
Accumulated Amortization	(565,475)	(460,144)
Customer Relationships
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	622,710	600,515
Accumulated Amortization	$ (337,800)	(275,993)
Customer Relationships | Minimum
Finite Lived Intangible Assets [Line Items]
Useful Life	6 years
Customer Relationships | Maximum
Finite Lived Intangible Assets [Line Items]
Useful Life	21 years
Trademarks
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 230,900	230,900
Accumulated Amortization	$ (227,520)	$ (184,151)
Trademarks | Minimum
Finite Lived Intangible Assets [Line Items]
Useful Life	4 years
Trademarks | Maximum
Finite Lived Intangible Assets [Line Items]
Useful Life	12 years
Noncompete Agreements
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 2,320
Accumulated Amortization	$ (155)
Noncompete Agreements | Minimum
Finite Lived Intangible Assets [Line Items]
Useful Life	5 years