Common Unit Repurchase and Retirement - Company's Repurchase Activities (Detail) - $ / shares shares in Thousands		1 Months Ended						3 Months Ended	98 Months Ended	99 Months Ended
		Jan. 31, 2021	Dec. 31, 2020		Nov. 30, 2020		Oct. 31, 2020	Dec. 31, 2019	Aug. 31, 2020	Sep. 30, 2020
Repurchase Plan
Capital Unit [Line Items]
Total Number of Units Purchased			730		1,553		308	2,591	14,400	17,697
Average Price Paid per Unit	[1]		$ 9.63		$ 9.83		$ 9.64	$ 9.75		$ 8.26
Maximum Number of Units that May Yet Be Purchased			4,539	[2]	5,269	[3]	5,422	4,539		5,730
Publicly Announced Plans or Programs As Part of Repurchase Plan
Capital Unit [Line Items]
Total Number of Units Purchased			730		153		308	1,191		14,622
Subsequent Event | Repurchase Plan
Capital Unit [Line Items]
Total Number of Units Purchased		429
Average Price Paid per Unit	[1]	$ 9.65
Maximum Number of Units that May Yet Be Purchased	[4],[5]	4,110
Subsequent Event | Publicly Announced Plans or Programs As Part of Repurchase Plan
Capital Unit [Line Items]
Total Number of Units Purchased		429

[1] Amount includes repurchase costs.

[2] On December 10, 2020, the Company purchased 0.4 million Common Units in a private transaction for aggregate consideration of approximately $4.2 million.  The purchase was made within the Company’s unit repurchase plan.

[3] On November 16, 2020, the Company purchased 1.4 million Common Units in a private transaction for aggregate consideration of approximately $13.8 million.  The purchase was made outside of the Company’s unit repurchase plan.

[4] Of the total available for repurchase, approximately 3.6 million units are available for repurchase in open market transactions and 0.5 million units are available for repurchase in privately-negotiated transactions, under the Repurchase Plan.

[5] On January 28, 2021, the Company purchased 0.1 million Common Units in a private transaction for aggregate consideration of approximately $1.3 million.  The purchase was made within the Company’s unit repurchase plan.