Partnership's Debt (Detail) - USD ($) $ in Thousands		Dec. 31, 2015	Sep. 30, 2015
Debt Instrument [Line Items]
Long-term debt, carrying Amount		$ 100,000	$ 100,000
Current maturities of long-term debt, carrying Amount		10,000	10,000
Long-term portion of debt, Carrying Amount		90,000	90,000
Long-term debt, fair value	[1]	100,000	100,000
Current maturities of long-term debt, fair value	[1]	10,000	10,000
Long-term portion of debt, fair value	[1]	90,000	90,000
$100 million Term Loan
Debt Instrument [Line Items]
Long-term debt, carrying Amount		100,000	100,000
Long-term debt, fair value	[1]	$ 100,000	$ 100,000

[1] The face amount of the Partnership's variable rate long-term debt approximates fair value.