Goodwill - Schedule of Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Balance, beginning of period	$ 367.1	$ 338.0
Additions		29.1
Adjustments	(0.3)
Balance, end of period	366.8	367.1
All Other
Goodwill [Roll Forward]
Balance, beginning of period	4.0	1.0
Additions		3.0
Adjustments	(0.3)
Balance, end of period	3.7	4.0
Churchill Downs \| Operating Segments
Goodwill [Roll Forward]
Balance, beginning of period	49.7	49.7
Additions		0.0
Adjustments	0.0
Balance, end of period	49.7	49.7
Online Wagering \| Operating Segments
Goodwill [Roll Forward]
Balance, beginning of period	148.2	148.2
Additions		0.0
Adjustments	0.0
Balance, end of period	148.2	148.2
Gaming \| Operating Segments
Goodwill [Roll Forward]
Balance, beginning of period	165.2	139.1
Additions		26.1
Adjustments	0.0
Balance, end of period	$ 165.2	$ 165.2

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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