Common Unit Repurchase Plans and Retirement - Additional Information (Detail) - USD ($) shares in Thousands	Jul. 30, 2015	Sep. 30, 2015	Jul. 31, 2013	Jul. 31, 2012
Capital Unit [Line Items]
Partnership's common units authorized for repurchase		6,044
Non Seasonal maximum borrowing capacity under revolving credit facility		$ 300,000,000
Third Amendment
Capital Unit [Line Items]
Availability required to repurchase common units	$ 45,000,000
Percentage of the maximum facility size on a historical proforma and forward-looking basis	15.00%
Non Seasonal maximum borrowing capacity under revolving credit facility	$ 300,000,000
Minimum fixed charge coverage ratio for distributions to unit holders or to repurchase common units	115.00%
Initial Common Units Authorized Plan III Common Units Repurchase Program
Capital Unit [Line Items]
Partnership's common units authorized for repurchase				3,000
Additional Common Units Authorized Plan III Common Units Repurchase Program
Capital Unit [Line Items]
Partnership's common units authorized for repurchase			1,900