Intangible Assets Subject to Amortization (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Sep. 30, 2017
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 388,965	$ 378,831
Accum. Amortization	288,106	273,613
Net	100,859	105,218
Customer Lists
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	356,437	346,784
Accum. Amortization	276,075	264,632
Net	80,362	82,152
Trade Names And Other Intangibles
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	32,528	32,047
Accum. Amortization	12,031	8,981
Net	$ 20,497	$ 23,066