Employee Incentive Plans - Amounts Recognized in Consolidated Financial Statements (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Allocation
Total unit-based compensation expense	$ 6.4	$ 7.4	$ 12.9	$ 16.2
Amount of related income tax benefit recognized in net income (loss)	1.5	1.7	3.0	3.8
Unit-based compensation, related income tax expense (benefit)	0.4	6.8	2.9	4.4
Restricted units
Allocation
Unit-based compensation, related income tax expense (benefit)	0.4	(6.8)	2.9	(4.4)
Cost of unit-based compensation charged to operating expense
Allocation
Total unit-based compensation expense	1.7	2.0	3.4	4.2
Cost of unit-based compensation charged to general and administrative expense
Allocation
Total unit-based compensation expense	$ 4.7	$ 5.4	$ 9.5	$ 12.0

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

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