Net Income Allocation and Per Unit Data (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Basic and Diluted Earnings Per Limited Partner:
Net income		$ 2,315	$ 30,182
Less General Partner’s interest in net income		15	175
Limited Partners’ interest in net income		2,300	30,007
Less dilutive impact of theoretical distribution of earnings under FASB ASC 260-10-45-60			4,740
Limited Partner’s interest in net income under FASB ASC 260-10-45-60		$ 2,300	$ 25,267
Per unit data:
Basic and diluted net income available to limited partners		$ 0.04	$ 0.53
Less dilutive impact of theoretical distribution of earnings under FASB ASC 260-10-45-60			0.08
Limited Partner’s interest in net income under FASB ASC 260-10-45-60	[1]	$ 0.04	$ 0.45
Weighted average number of Limited Partner units outstanding		52,905	55,888

[1] See Note 15 - Earnings Per Limited Partner Unit.