Goodwill and Other Intangible Assets - Goodwill (Details) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($)
Goodwill [Roll Forward]
Balances as of December 31, 2018	$ 338.0
Additions	25.8
Balances as of March 31, 2019	363.8
Churchill Downs
Goodwill [Roll Forward]
Balances as of December 31, 2018	49.7
Additions	0.0
Balances as of March 31, 2019	49.7
Online Wagering
Goodwill [Roll Forward]
Balances as of December 31, 2018	148.2
Additions	0.0
Balances as of March 31, 2019	148.2
Gaming
Goodwill [Roll Forward]
Balances as of December 31, 2018	139.1
Additions	25.8
Balances as of March 31, 2019	164.9
All Other
Goodwill [Roll Forward]
Balances as of December 31, 2018	1.0
Additions	0.0
Balances as of March 31, 2019	$ 1.0

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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

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