Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Maturities of time deposits, description	24 months
Capitalized computer software, additions	$ 28,200,000	$ 48,300,000
Capitalized computer software, gross	105,300,000	114,600,000
Marketing and advertising expense	16,200,000	48,100,000	$ 51,200,000
Accounts receivable	0	900,000
Affiliated Entity
Market development fees	$ 50,200,000	$ 11,300,000
Minimum
Contractual remittance schedule range of days	1 day
Maximum
Contractual remittance schedule range of days	3 days