Revolving Line of Credit - Additional Information (Detail) (USD $)	9 Months Ended
	Jun. 30, 2014
Line of Credit Facility [Line Items]
Unsecured revolving line of credit	$ 200,000,000
Revolving credit facility, expiration date	Sep. 28, 2016
Revolving credit facility, interest rate description	Interest on amounts borrowed under the credit facility is based on (i) a base rate, which is the greater of (a) the prime rate and (b) the Federal Funds rate plus 0.50% or (ii) LIBOR plus an applicable margin. The margin on LIBOR borrowings ranges from 1.000% to 1.625% and is determined based on our consolidated leverage ratio.
Revolving credit facility, utilization fees, percentage of total credit facility commitment to exceed	50.00%
Credit facility restrictive covenant, maximum consolidated leverage ratio	3.0
Credit facility restrictive covenant, minimum fixed charge ratio	2.5
Borrowings outstanding	$ 83,000,000
Interest rate of borrowings outstanding	1.282%
Libor | Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	1.00%
Libor | Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	1.625%
Federal Fund Rate
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	0.50%