Notes Payable and Indebtedness - Summary (Details) $ in Millions	9 Months Ended
Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Feb. 08, 2019
Debt Maturing Within One Year:
Principal amount, current maturities of long-term debt	$ 25.3
Principal Amount		$ 82.0
Debt Issuance Costs and Discount*	0.0	0.1
Carrying value, current maturities of long-term debt	25.3
Carrying Value	25.3	81.9
Debt Maturing After One Year:
Principal Amount	3,362.1	3,961.0
Debt Issuance Costs and Discount*	104.6	142.1
Carrying Value	3,257.5	3,818.9
Total debt
Principal amount, long-term debt	3,387.4
Principal amount, long-term and short-term debt		4,043.0
Debt Issuance Costs and Discount	104.6	142.2
Carrying Value	3,282.8
Carrying Value		3,900.8
Bridge Facility \| Bridge Loan
Debt Maturing Within One Year:
Principal amount, short-term debt		63.0
Debt Issuance Costs and Discount*		0.1
Carrying value, short-term debt		62.9
New Term Loan Facility \| Line of Credit
Debt Maturing After One Year:
Principal Amount	2,492.1	2,511.0
Debt Issuance Costs and Discount*	80.9	98.3
Carrying Value	2,411.2	2,412.7
New Term Loan Facility \| Line of Credit \| Secured Debt
Debt Maturing Within One Year:
Principal amount, current maturities of long-term debt	25.3	19.0
Debt Issuance Costs and Discount*	0.0	0.0
Carrying value, current maturities of long-term debt	25.3	19.0
New Revolving Facility \| Line of Credit \| Revolving Credit Facility
Debt Maturing After One Year:
Principal Amount	0.0	0.0
Debt Issuance Costs and Discount*	0.0	0.0
Carrying Value	$ 0.0	0.0
Total debt
Maximum ratio of first lien net indebtedness to consolidated EBITDA	6.75
Applicable threshold for maximum ratio of first lien net indebtedness to consolidated EBITDA (as a percent)	35.00%
New Senior Secured Notes \| Secured Debt
Debt Maturing After One Year:
Principal Amount	$ 420.0	700.0
Debt Issuance Costs and Discount*	8.6	15.8
Carrying Value	411.4	684.2
Total debt
Interest rate on debt instrument (as a percent)			6.875%
New Senior Unsecured Notes \| Unsecured Debt Excluding Current Maturities
Debt Maturing After One Year:
Principal Amount	450.0	750.0
Debt Issuance Costs and Discount*	15.1	28.0
Carrying Value	$ 434.9	$ 722.0
New Senior Unsecured Notes \| Unsecured Debt
Total debt
Interest rate on debt instrument (as a percent)			10.25%

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