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
		Jul. 31, 2021	Jun. 30, 2021	May 31, 2021		Jun. 30, 2021	Mar. 31, 2021		Dec. 31, 2020		Aug. 31, 2020	Sep. 30, 2020	Apr. 30, 2021	[3]
Repurchase Plan
Capital Unit [Line Items]
Total Number of Units Purchased			259	309		568	538		2,591		14,400	17,697
Average Price Paid per Unit	[1]		$ 11.06	$ 10.83		$ 10.94	$ 9.67		$ 9.75			$ 8.26
Maximum Number of Units that May Yet Be Purchased			3,433	3,692	[2]	3,433	4,001	[3]	4,539	[4],[5]		5,730	4,001
Repurchase Plan | Subsequent Event
Capital Unit [Line Items]
Total Number of Units Purchased		25
Average Price Paid per Unit	[1]	$ 11.27
Maximum Number of Units that May Yet Be Purchased	[6]	3,408
Publicly Announced Plans or Programs As Part of Repurchase Plan
Capital Unit [Line Items]
Total Number of Units Purchased			259	309		568	538		1,191			14,622
Publicly Announced Plans or Programs As Part of Repurchase Plan | Subsequent Event
Capital Unit [Line Items]
Total Number of Units Purchased		25

[1] Amount includes repurchase costs.

[2] On May 28, 2021, the Company purchased 0.3 million Common Units in a private transaction for aggregate consideration of approximately $2.8 million.  The purchase was made within the Company’s unit repurchase plan.

[3] 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.

[4] 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.

[5] 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.

[6] Of the total available for repurchase, approximately 3.1 million units are available for repurchase in open market transactions and 0.3 million units are available for repurchase in privately-negotiated transactions, under the Repurchase Plan.