Long-Term Debt and Bank Facility Borrowings - Additional Information (Detail) (USD $)	0 Months Ended	6 Months Ended
	Jan. 14, 2014	Mar. 31, 2015	Sep. 30, 2014
Debt Instrument [Line Items]
Hedging positions and payable amounts secured under credit facility		12,200,000	$ 14,900,000
Letters of credit issued		55,400,000	52,800,000
Availability in compliance with the fixed charge coverage ratio		232,400,000	149,600,000
Revolving Credit Facility
Debt Instrument [Line Items]
Revolving credit facility outstanding		0	0
Second Amendment
Debt Instrument [Line Items]
Non Seasonal maximum borrowing capacity under revolving credit facility	300,000,000
Maximum borrowing capacity (heating season December to April) under revolving credit facility	450,000,000
Issuance of line of credit for working capital purposes	100,000,000
Alternate revolving credit facility expiry	Jan. 14, 2019
Revolving credit facility expiry	Jun. 01, 2017
Additional revolving credit	100,000,000
Facility size that can be increased without consulting bank group	100,000,000
Line of credit facility description		All outstanding amounts owed under the second amended and restated credit facility become due and payable on the facility termination date of June 1, 2017. If the Partnership has repaid, prepaid or otherwise defeased at least $100 million of our 8.875% Senior Notes and Availability is equal to or greater than the aggregate amount required to repay the remaining outstanding 8.875% Senior Notes ("Payoff Amount"), then the facility termination date is January 14, 2019.
Description of variable rate		The interest rate on the second amended and restated credit facility is LIBOR plus (i) 1.75% (if Availability, as defined in the agreement is greater than or equal to $150 million), or (ii) 2.00% (if Availability is greater than $75 million but less than $150 million), or (iii) 2.25% (if Availability is less than or equal to $75 million). The Commitment Fee on the unused portion of the facility is 0.30% per annum.
Condition one, additional interest rate based on LIBOR	1.75%
Condition two, additional interest rate based on LIBOR	2.00%
Condition three, additional interest rate based on LIBOR	2.25%
Minimum availability, condition one	150,000,000
Maximum availability, condition two	150,000,000
Minimum availability, condition two	75,000,000
Maximum availability, condition three	75,000,000
Commitment fee on the unused portion of the facility	0.30%
Availability percentage to maximum facility size	12.50%
Minimum fixed charge coverage ratio	110.00%
Availability required to make acquisition	40,000,000
Availability required to pay distributions	45,000,000
Percentage of the maximum facility size on a historical proforma and forward-looking basis	15.00%
Minimum fixed charge coverage ratio for distributions to unit holders or to repurchase common units	115.00%
8.875% Senior Notes
Debt Instrument [Line Items]
Interest accrued by public notes for each year		8.875%
8.875% Senior Notes | Second Amendment
Debt Instrument [Line Items]
Amount required to repaid, prepaid or defeased	$ 100,000,000
Interest accrued by public notes for each year	8.875%