Consolidated Statements of Partners' Capital - USD ($) shares in Thousands, $ in Thousands		Total		Common Stock	General Partner	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Sep. 30, 2012		$ 260,145		$ 286,819	$ 97	$ (26,771)
Beginning Balance, unit at Sep. 30, 2012				61,002	326
Net income		29,906		$ 29,747	$ 159
Unrealized gain (loss) on pension plan obligation	[1]	6,337	[2]			6,337
Tax effect of unrealized gain (loss) on pension plan obligation		(2,577)				(2,577)
Distributions	[3]	(19,313)		$ (19,060)	(253)
Retirement of units, shares	[4]			(3,284)
Retirement of units	[4]	(15,217)		$ (15,217)
Ending Balance at Sep. 30, 2013		259,281		$ 282,289	$ 3	(23,011)
Ending Balance, Unit at Sep. 30, 2013				57,718	326
Net income		36,084		$ 35,881	$ 203
Unrealized gain (loss) on pension plan obligation	[1]	(1,070)	[2]			(1,070)
Tax effect of unrealized gain (loss) on pension plan obligation		463				463
Distributions	[3]	(19,850)		$ (19,539)	(311)
Retirement of units, shares	[4]			(313)
Retirement of units	[4]	(1,663)		$ (1,663)
Ending Balance at Sep. 30, 2014		273,245		$ 296,968	$ (105)	(23,618)
Ending Balance, Unit at Sep. 30, 2014				57,405	326
Net income		37,556		$ 37,344	$ 212
Unrealized gain (loss) on pension plan obligation	[1]	1,827	[2]			1,827
Tax effect of unrealized gain (loss) on pension plan obligation		(753)				(753)
Distributions	[3]	(21,298)		$ (20,908)	(390)
Retirement of units, shares	[4]			(123)
Retirement of units	[4]	(691)		$ (691)
Ending Balance at Sep. 30, 2015		$ 289,886		$ 312,713	$ (283)	$ (22,544)
Ending Balance, Unit at Sep. 30, 2015				57,282	326

[1] These items are included in the computation of net periodic pension cost. See Note 12 - Employee Benefit Plan.

[2] These items are included in the computation of net periodic pension cost. See Note 12 - Employee Benefit Plans.

[3] See Note 3 - Quarterly Distributions of Available Cash.

[4] See Note 4 - Common Unit Repurchase Plan and Retirement.