Revenue from Contracts with Customers (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 604,234,000	$ 530,587,000
Bad debt expense	0	0
Contract assets	0	0
Contract liabilities	0	0
Deferred contract costs	0	0
Revenue from performance obligations related to prior periods	0	0
Transaction Fees
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	598,760,000	526,942,000
Referral Fees
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	5,474,000	3,645,000
Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 0	$ 0