Employee Incentive Plans - Amounts Recognized in Consolidated Financial Statements (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Allocation
Total unit-based compensation expense	$ 6.4	$ 8.4	$ 19.3	$ 24.6
Amount of related income tax benefit recognized in net income (loss)	1.5	2.0	4.5	5.8
Unit-based compensation	0.2	1.6	3.1	6.0
Restricted units
Allocation
Unit-based compensation	0.2	1.6	3.1	6.0
Cost of unit-based compensation charged to operating expense
Allocation
Total unit-based compensation expense	1.5	2.0	4.9	6.2
Cost of unit-based compensation charged to general and administrative expense
Allocation
Total unit-based compensation expense	$ 4.9	$ 6.4	$ 14.4	$ 18.4

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

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