Common Unit Repurchase Plans and Retirement - Company's Repurchase Activities (Detail) - $ / shares shares in Thousands		1 Months Ended			3 Months Ended				12 Months Ended	131 Months Ended	132 Months Ended
		Nov. 30, 2024	[2]	Oct. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2024	May 31, 2023	Sep. 30, 2023
Repurchase Plan
Capital Unit [Line Items]
Total Number of Units Purchased					187	598	218	13	1,016	20,500	25,422
Average Price Paid per Unit	[1]				$ 11.02	$ 10.86	$ 10.92	$ 11.27	$ 10.91		$ 8.82
Maximum Number of Units that May Yet Be Purchased					1,552	1,739	2,337	2,555	1,552		2,568
Repurchase Plan | Subsequent Event
Capital Unit [Line Items]
Total Number of Units Purchased		5		3
Average Price Paid per Unit	[1]	$ 11.12		$ 11.25
Maximum Number of Units that May Yet Be Purchased		1,544		1,549
Publicly Announced Plans or Programs As Part of Repurchase Plan
Capital Unit [Line Items]
Total Number of Units Purchased					187	598	218	13	1,016		20,534
Publicly Announced Plans or Programs As Part of Repurchase Plan | Subsequent Event
Capital Unit [Line Items]
Total Number of Units Purchased		5		3

[1] Amounts include repurchase costs.

[2] Of the total available for repurchase, approximately 1.2 million are available for repurchase in open market transactions and 0.3 million are available for repurchase in privately-negotiated transactions.