Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Total assets	$ 2,551.0	$ 1,725.2
Total liabilities	2,040.0	1,251.9
Advertising and marketing expense	41.8	28.8	$ 24.8
Oak Grove
Variable Interest Entity [Line Items]
Total assets	62.1
Total liabilities	$ 9.3
Grandstands and buildings | Minimum
Variable Interest Entity [Line Items]
Property, plant, and equipment, useful life	10 years
Grandstands and buildings | Maximum
Variable Interest Entity [Line Items]
Property, plant, and equipment, useful life	40 years
Equipment | Minimum
Variable Interest Entity [Line Items]
Property, plant, and equipment, useful life	2 years
Equipment | Maximum
Variable Interest Entity [Line Items]
Property, plant, and equipment, useful life	10 years
Furniture and fixtures | Minimum
Variable Interest Entity [Line Items]
Property, plant, and equipment, useful life	2 years
Furniture and fixtures | Maximum
Variable Interest Entity [Line Items]
Property, plant, and equipment, useful life	10 years
Tracks and other improvements | Minimum
Variable Interest Entity [Line Items]
Property, plant, and equipment, useful life	10 years
Tracks and other improvements | Maximum
Variable Interest Entity [Line Items]
Property, plant, and equipment, useful life	20 years
Internally developed and purchased third party software
Variable Interest Entity [Line Items]
Capitalized computer software developed or acquired for internal use	$ 9.8	9.7	7.2
Capitalized computer software developed or acquired for internal use, amortization expense	$ 8.8	$ 7.3	$ 6.3
Internally developed and purchased third party software | Maximum
Variable Interest Entity [Line Items]
Property, plant, and equipment, useful life	3 years
WKY Development, LLC
Variable Interest Entity [Line Items]
Ownership percentage	95.00%