Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Common Unit Repurchase and Retirement - Company's Repurchase Activities (Parenthetical) (Detail) - shares shares in Millions	3 Months Ended
	Mar. 31, 2019	Jul. 30, 2019	Sep. 30, 2018
Private Transaction
Capital Unit [Line Items]
Company's common units repurchased	1.2
Common Stock Available for Repurchase Under Open Market Transactions
Capital Unit [Line Items]
Company's common units authorized for repurchase			8.4
Common Stock Available for Repurchase Under Open Market Transactions \| Subsequent Event
Capital Unit [Line Items]
Company's common units authorized for repurchase		0.3
Common Stock Available for Repurchase Under Privately Negotiated Transactions
Capital Unit [Line Items]
Company's common units authorized for repurchase			2.5
Common Stock Available for Repurchase Under Privately Negotiated Transactions \| Subsequent Event
Capital Unit [Line Items]
Company's common units authorized for repurchase		1.3