Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands			1 Months Ended				3 Months Ended		9 Months Ended		67 Months Ended
		Jul. 02, 2018	Jul. 31, 2018	Jun. 30, 2018	May 31, 2018	Apr. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2018	Jun. 30, 2017	Jan. 31, 2018
Subsequent Event [Line Items]
Repayments of existing term loan									$ 7,500,000	$ 13,700,000
Repayments of revolving credit facility borrowings									$ 118,604,000
Plan III Common Units Repurchase Program
Subsequent Event [Line Items]
Company's common units repurchased and retired				261	202	626	1,089	1,281			2,700
Average price paid per unit	[1]			$ 9.56	$ 9.64	$ 9.71	$ 9.66	$ 9.38
Subsequent Event | Plan III Common Units Repurchase Program
Subsequent Event [Line Items]
Company's common units repurchased and retired	[2]		125
Average price paid per unit	[1],[2]		$ 9.72
Subsequent Event | Dividend Declared
Subsequent Event [Line Items]
Distribution declared			0.1175
Partners capital projected distribution amount on annualized basis			0.47
Minimum dividend distribution per unit			$ 0.0675
Amount to paid to common unit holders			$ 6,300,000
Amount to paid to the General Partner			200,000
Incentive distribution to the General Partner			170,000
Incentive distributions to management			$ 200,000
Dividend payable date			Aug. 07, 2018
Dividend record date			Jul. 30, 2018
Subsequent Event | Fourth Amendment
Subsequent Event [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		$ 25,000,000
Revolving credit facility expiry		Jul. 02, 2023
Repayments of revolving credit facility borrowings		$ 33,700,000
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%
Minimum fixed charge coverage ratio for distributions to unit holders or to repurchase common units		115.00%
Subsequent Event | Term Loan | Fourth Amendment
Subsequent Event [Line Items]
Outstanding senior notes		$ 100,000,000
Senior secured term loan maturity period		5 years
Repayments of existing term loan		$ 66,300,000

[1] Amount includes repurchase costs.

[2] See Note 14 - Subsequent Events.