Estimated Compensation Expenses For RSU Award (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation cost (included in operating expenses)	$ 587	$ 508	$ 304
Tax benefit recognized	140	108	56
Net compensation cost	447	400	248
Restricted Stock Units
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Tax benefit recognized	720
Net compensation cost	1,163
Total compensation cost for non-vested awards not yet recognized	2,346
Weighted-average years to be recognized	1 year
Restricted Stock Units | Other long-term liabilities
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Accrued compensation cost included in other long-term liabilities at year end	1,883
Restricted Stock Units | Operating Expenses
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Compensation cost (included in operating expenses)	$ 1,883