Income Taxes - Reorganization Transactions - (Details) - USD ($) $ in Millions		12 Months Ended
	Apr. 01, 2016	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income taxes
Current tax receivables related to transactions prior to Reorganization Transactions		$ 93.1	$ 93.1
Unrecognized tax positions			119.3	$ 118.1
Indemnification receivable			26.1	25.0
Total state and local distribution taxes reported		92.1
Net adjustments to pre-reorganization indemnification receivables or payables and unrecognized tax benefits			$ 1.2	$ 0.0	$ 1.5
Reorganization Transactions on April 1, 2016
Income taxes
Current tax receivables recorded	$ 72.8
Unrecognized tax positions	116.6
Indemnification payable	28.6
Certain tax related liabilities incurred	95.4
Expected federal tax benefit on distribution taxes	$ 33.4
Capital Distributions		$ 2.1