Employee Incentive Plans - Amounts Recognized in Consolidated Financial Statements (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Allocation
Compensation expense	$ 6.5	$ 8.8
Amount of related income tax benefit recognized in net income (loss)	1.5	2.1
Restricted units
Allocation
Amount of related income tax benefit recognized in net income (loss)	(2.5)	2.4
Cost of unit-based compensation charged to operating expense
Allocation
Compensation expense	1.7	2.2
Cost of unit-based compensation charged to general and administrative expense
Allocation
Compensation expense	$ 4.8	$ 6.6

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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Balance Type:	debit
Period Type:	duration