Financial Instruments and Risk Management - Tax Receivable Agreement Narrative (Details) $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Tax Receivable Agreement, estimated payments, undiscounted	$ 191.5			$ 191.5
Fair value of the estimated liability included as an adjustment to additional pain in capital			$ 133.4
Accretion expense, Tax Receivable Agreement	1.6	$ 2.7		3.3	$ 18.8
Unrealized gain (loss) recorded in other comprehensive income	$ 2.2	$ (11.1)		(3.1)	$ 5.1
Tax Receivable Agreement, effect of one percentage point change on fair value				$ 11.0
Measurement Input, Discount Rate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Tax Receivable Agreement, measurement input	0.031			0.031
Additional Paid in Capital
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of the estimated liability included as an adjustment to additional pain in capital			$ 133.4			$ 133.4