Geographic Information (Revenues and Long-Lived Assets by Geographic Region) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 605,080	$ 606,443	$ 563,114	$ 572,848	$ 551,406	$ 554,669	$ 507,170	$ 461,901	$ 2,347,485	$ 2,075,146	$ 1,565,340
Property, Plant and Equipment, Net	39,183				35,784				39,183	35,784	25,209
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									2,032,260	1,776,414	1,304,794
Property, Plant and Equipment, Net	32,881				29,001				32,881	29,001	18,953
International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									315,225	298,732	260,546
Property, Plant and Equipment, Net	$ 6,302				$ 6,783				$ 6,302	$ 6,783	$ 6,256