Segment Information - Reconciliation of Comprehensive Income to Adjusted EBITDA (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
	Aug. 31, 2018	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Comprehensive income attributable to CDI										$ 137.5	$ 353.2	$ 140.4
Foreign currency translation, net of tax										0.0	(0.6)	0.1
Change in pension benefits, net of tax										0.0	0.2	0.0
Net income attributable to CDI										137.5	352.8	140.5
Net income before noncontrolling interest										(0.3)	0.0	0.0
Net income										137.2	352.8	140.5
Loss (income) from discontinued operations, net of tax		$ 0.5	$ 0.4	$ 1.2	$ 0.3	$ (4.1)	$ 1.7	$ 0.1	$ (167.9)	2.4	(170.2)	(18.1)
Income from continuing operations, net of tax		$ 4.2	$ 15.2	$ 108.3	$ 11.9	$ 7.3	58.0	$ 103.2	$ 14.1	139.6	182.6	122.4
Depreciation and amortization										96.4	63.6	97.1
Loss on extinguishment of debt										0.0	0.0	20.7
Income tax provision (benefit)										56.8	51.3	(19.9)
EBITDA										363.7	337.6	228.5
Stock-based compensation expense										23.8	21.1	27.1
Legal reserves										3.6	0.0	0.0
Changes in fair value of Midwest Gaming's interest rate swaps										12.4	0.0	0.0
Recapitalization Costs										4.7	0.0	0.0
Gain on Ocean Downs/Saratoga transaction	$ (54.9)						$ (54.9)			0.0	(54.9)	0.0
Impairment of tangible and other intangible assets										0.0	0.0	21.7
Total adjustments to EBITDA										87.7	(8.8)	57.7
Adjusted EBITDA										451.4	328.8	286.2
Churchill Downs
Segment Reporting Information [Line Items]
Adjusted EBITDA										137.7	102.4	89.0
Online Wagering
Segment Reporting Information [Line Items]
Adjusted EBITDA										66.3	79.0	69.9
Gaming
Segment Reporting Information [Line Items]
Adjusted EBITDA										280.9	174.0	148.6
All Other
Segment Reporting Information [Line Items]
Adjusted EBITDA										484.9	355.4	307.5
Total Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA										(33.5)	(26.6)	(21.3)
Continuing Operations
Segment Reporting Information [Line Items]
Depreciation and amortization										96.4	63.6	56.0
Interest expense										70.9	40.1	49.3
Loss on extinguishment of debt										0.0	0.0	20.7
Income tax provision (benefit)										56.8	51.3	(19.9)
Stock-based compensation expense										23.8	17.7	16.0
Other, net										0.4	(0.6)	0.5
Pre-opening expense										5.1	4.8	0.5
Interest, depreciation and amortization expense related to equity investments										32.6	13.9	16.7
Other charges and recoveries, net										(0.2)	0.0	0.0
Gain on Ocean Downs/Saratoga transaction										0.0	(54.9)	0.0
Transaction expense, net										5.3	10.3	2.3
Impairment of tangible and other intangible assets										$ 0.0	$ 0.0	$ 21.7