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		9 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Basic and Diluted Earnings Per Limited Partner:
Net income (loss)		$ (10,587)	$ (12,054)	$ 85,281	$ 110,970
Less General Partner's interest in net income (loss)		(93)	(98)	726	879
Net income (loss) available to limited partners		(10,494)	(11,956)	84,555	110,091
Less dilutive impact of theoretical distribution of earnings	[1]			13,677	18,545
Limited Partner's interest in net income (loss)		$ (10,494)	$ (11,956)	$ 70,878	$ 91,546
Per unit data:
Basic and diluted net income (loss) available to limited partners		$ (0.29)	$ (0.30)	$ 2.24	$ 2.69
Less dilutive impact of theoretical distribution of earnings	[1]			0.36	0.45
Limited Partner's interest in net income (loss)		$ (0.29)	$ (0.30)	$ 1.88	$ 2.24
Weighted average number of Limited Partner units outstanding		36,781	40,041	37,739	40,897

[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.