Fair Value Disclosure - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Sep. 30, 2013
Fair Value, Inputs, Level 2 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of long-term debt	$ 475,000	$ 491,000
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Line of credit facility amount outstanding	5,000
Line of credit facility fair value of amount outstanding	$ 5,000