Fair Value Measurements - Carrying Amounts and Estimated Fair Values by Input Level (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Jan. 19, 2017
Financial assets:
Equity securities	$ 143.1	$ 40.5
Senior Notes | 5.625% Notes
Financial liabilities:
Interest rate	5.625%	5.625%	5.625%
Carrying Amount
Financial assets:
Cash and cash equivalents	$ 1,853.8	$ 437.4
Equity securities	143.1	40.5
Held-to-maturity securities	6.7	6.7
Promissory notes	15.1	15.1
Financial liabilities:
Other liabilities	10.1	20.3
Puts and calls related to certain Barstool Sports shares	0.3
Carrying Amount | Secured Credit Facility
Financial liabilities:
Long-term debt	1,600.3	1,896.5
Carrying Amount | Senior Notes | 5.625% Notes
Financial liabilities:
Long-term debt	399.5	399.4
Carrying Amount | Convertible Notes Payable
Financial liabilities:
Long-term debt	239.8
Carrying Amount | Notes Payable, Other Payables
Financial liabilities:
Long-term debt	73.0	89.2
Fair Value
Financial assets:
Cash and cash equivalents	1,853.8	437.4
Equity securities	143.1	40.5
Held-to-maturity securities	6.7	6.7
Promissory notes	15.1	15.1
Financial liabilities:
Other liabilities	10.1	20.3
Puts and calls related to certain Barstool Sports shares	0.3
Fair Value | Secured Credit Facility
Financial liabilities:
Long-term debt	1,609.3	1,930.6
Fair Value | Senior Notes | 5.625% Notes
Financial liabilities:
Long-term debt	418.0	426.0
Fair Value | Convertible Notes Payable
Financial liabilities:
Long-term debt	1,274.5
Fair Value | Notes Payable, Other Payables
Financial liabilities:
Long-term debt	72.8	89.7
Level 1
Financial assets:
Cash and cash equivalents	1,853.8	437.4
Equity securities	0.0	0.0
Held-to-maturity securities	0.0	0.0
Promissory notes	0.0	0.0
Financial liabilities:
Other liabilities	0.0	0.0
Puts and calls related to certain Barstool Sports shares	0.0
Level 1 | Secured Credit Facility
Financial liabilities:
Long-term debt	1,609.3	1,930.6
Level 1 | Senior Notes | 5.625% Notes
Financial liabilities:
Long-term debt	418.0	426.0
Level 1 | Convertible Notes Payable
Financial liabilities:
Long-term debt	1,274.5
Level 1 | Notes Payable, Other Payables
Financial liabilities:
Long-term debt	0.0	0.0
Level 2
Financial assets:
Cash and cash equivalents	0.0	0.0
Equity securities	143.1	40.5
Held-to-maturity securities	6.7	6.7
Promissory notes	15.1	15.1
Financial liabilities:
Other liabilities	2.8	2.8
Puts and calls related to certain Barstool Sports shares	0.3
Level 2 | Secured Credit Facility
Financial liabilities:
Long-term debt	0.0	0.0
Level 2 | Senior Notes | 5.625% Notes
Financial liabilities:
Long-term debt	0.0	0.0
Level 2 | Convertible Notes Payable
Financial liabilities:
Long-term debt	0.0
Level 2 | Notes Payable, Other Payables
Financial liabilities:
Long-term debt	72.8	89.7
Level 3
Financial assets:
Cash and cash equivalents	0.0	0.0
Equity securities	0.0	0.0
Held-to-maturity securities	0.0	0.0
Promissory notes	0.0	0.0
Financial liabilities:
Other liabilities	7.3	17.5
Puts and calls related to certain Barstool Sports shares	0.0
Level 3 | Secured Credit Facility
Financial liabilities:
Long-term debt	0.0	0.0
Level 3 | Senior Notes | 5.625% Notes
Financial liabilities:
Long-term debt	0.0	0.0
Level 3 | Convertible Notes Payable
Financial liabilities:
Long-term debt	0.0
Level 3 | Notes Payable, Other Payables
Financial liabilities:
Long-term debt	$ 0.0	$ 0.0