Earnings Per Limited Partner Unit - Net Income Allocation and Per Unit Data (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Basic and Diluted Earnings Per Limited Partner:
Net income		$ 37,860	$ 27,755
Less General Partner’s interest in net income		296	192
Net income available to limited partners		37,564	27,563
Less dilutive impact of theoretical distribution of earnings	[1]	6,332	4,351
Limited Partner’s interest in net income		$ 31,232	$ 23,212
Per unit data:
Basic and diluted net income available to limited partners		$ 0.89	$ 0.58
Less dilutive impact of theoretical distribution of earnings	[1]	0.15	0.09
Limited Partner’s interest in net income	[2]	$ 0.74	$ 0.49
Weighted average number of Limited Partner units outstanding		42,246	47,266

[1] In any accounting period where the Company’s aggregate net income exceeds its aggregate distribution for such period, the Company is required to present net income per limited partner unit as if all of the earnings for the period were distributed, based on the terms of the Partnership agreement, regardless of whether those earnings would actually be distributed during a particular period from an economic or practical perspective. This allocation does not impact the Company’s overall net income or other financial results.

[2] See Note 16 - Earnings Per Limited Partner Unit.