Significant Accounting Policies - Revenue Disaggregation and Customer-Related Liabilities (Details) $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($) agreement type	Dec. 31, 2020 USD ($)
Disaggregation of Revenue [Line Items]
Contract with customer, liability, number of liability types | type	3
Online Sports Betting and iGaming Market Access
Disaggregation of Revenue [Line Items]
Customer-related liabilities	$ 54.4	$ 52.7
Number of operator agreements containing ordinary shares and warrants | agreement	2
Loyalty Credit Obligation
Disaggregation of Revenue [Line Items]
Customer-related liabilities	$ 35.0	35.8
Customer-related liabilities, term	6 months
Advance Payments on Goods and Services Yet to Be Provided and Unpaid Wagers
Disaggregation of Revenue [Line Items]
Customer-related liabilities	$ 91.6	47.1
Customer-related liabilities, long-term	$ 0.0	$ 0.5