Net Income Allocation and Per Unit Data (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Basic and Diluted Earnings Per Limited Partner:
Net income	$ 9,752		$ 2,931
Less General Partners' interest in net income	53		15
Net income available to limited partners	9,699		2,916
Less dilutive impact of theoretical distribution of earnings under FASB ASC 260-10-45-60	762
Limited Partner's interest in net income under FASB ASC 260-10-45-60	$ 8,937		$ 2,916
Per unit data:
Basic and diluted net income available to limited partners	0.16		0.05
Less dilutive impact of theoretical distribution of earnings under FASB ASC 260-10-45-60	0.01
Limited Partner's interest in net income under FASB ASC 260-10-45-60	0.15	[1]	0.05	[1]
Weighted average number of Limited Partner units outstanding	60,556		64,189

[1] See Note 13 Earnings (Loss) Per Limited Partner Unit.