Common Unit Repurchase and Retirement - Company's Repurchase Activities (Parenthetical) (Detail) - shares shares in Millions	3 Months Ended
	Dec. 31, 2019	Jul. 31, 2020	May 31, 2020	Apr. 30, 2020	Feb. 29, 2020	Jan. 31, 2020
Capital Unit [Line Items]
Company's common units authorized for repurchase			3.6	0.1	1.1	0.1
Private Transaction
Capital Unit [Line Items]
Company's common units repurchased	0.6
Common Stock Available for Repurchase Under Open Market Transactions
Capital Unit [Line Items]
Company's common units authorized for repurchase			2.5
Common Stock Available for Repurchase Under Open Market Transactions | Subsequent Event
Capital Unit [Line Items]
Company's common units authorized for repurchase		1.0
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		1.1