Intangible Assets Subject to Amortization (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 391,515	$ 378,831
Accum. Amortization	293,071	273,613
Net	98,444	105,218
Customer Lists
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	358,776	346,784
Accum. Amortization	279,990	264,632
Net	78,786	82,152
Trade Names And Other Intangibles
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	32,739	32,047
Accum. Amortization	13,081	8,981
Net	$ 19,658	$ 23,066