Fair Value Measurements - Significant Unobservable Inputs For Level 3 Assets and Liabilities (Details) $ in Millions	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)
Gaming licenses
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Indefinite-lived intangible assets, fair value	$ 568.0	$ 568.0
Trademarks
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Indefinite-lived intangible assets, fair value	216.5	$ 216.5
Level 3 | Gaming licenses
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Indefinite-lived intangible assets, fair value	568.0
Level 3 | Trademarks
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Indefinite-lived intangible assets, fair value	$ 216.5
Level 3 | Discounted cash flow | Discount rate | Gaming licenses | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Indefinite-lived intangible assets, measurement input		0.1325
Level 3 | Discounted cash flow | Discount rate | Gaming licenses | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Indefinite-lived intangible assets, measurement input		0.140
Level 3 | Discounted cash flow | Discount rate | Trademarks | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Indefinite-lived intangible assets, measurement input		0.1325
Level 3 | Discounted cash flow | Discount rate | Trademarks | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Indefinite-lived intangible assets, measurement input		0.140
Level 3 | Discounted cash flow | Long-term revenue growth rate | Gaming licenses
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Indefinite-lived intangible assets, measurement input		0.020
Level 3 | Discounted cash flow | Long-term revenue growth rate | Trademarks
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Indefinite-lived intangible assets, measurement input		0.020
Level 3 | Discounted cash flow | Pretax royalty rate | Trademarks | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Indefinite-lived intangible assets, measurement input		0.010
Level 3 | Discounted cash flow | Pretax royalty rate | Trademarks | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Indefinite-lived intangible assets, measurement input		0.020
Plainridge Park Casino | Level 3 | Discounted cash flow | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration, measurement input	0.0567