Common Unit Repurchase and Retirement - Company's Repurchase Activities (Parenthetical) (Detail) - USD ($) shares in Millions, $ in Millions	Jan. 28, 2021	Dec. 10, 2020	Nov. 16, 2020	Apr. 30, 2021	Aug. 31, 2020	Jul. 31, 2020
Capital Unit [Line Items]
Company's common units authorized for repurchase					6.0	2.0
Private Transaction
Capital Unit [Line Items]
Company's common units repurchased	0.1	0.4	1.4
Aggregate consideration paid for common units purchased	$ 1.3	$ 4.2	$ 13.8
Common Stock Available for Repurchase Under Open Market Transactions
Capital Unit [Line Items]
Company's common units authorized for repurchase					4.9
Common Stock Available for Repurchase Under Open Market Transactions | Subsequent Event
Capital Unit [Line Items]
Company's common units authorized for repurchase				3.5
Common Stock Available for Repurchase Under Privately Negotiated Transactions
Capital Unit [Line Items]
Company's common units authorized for repurchase					1.1
Common Stock Available for Repurchase Under Privately Negotiated Transactions | Subsequent Event
Capital Unit [Line Items]
Company's common units authorized for repurchase				0.5