Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue	$ 396,361	$ 389,050	$ 727,916	$ 662,305
Service Revenue [Member]
Revenue	252,748	234,139	458,778	417,262
Commission Revenue [Member]
Revenue	129,334	125,465	233,309	218,950
Fees Revenue [Member]
Revenue	123,414	108,674	225,469	198,312
Inventory Sales Revenue [Member]
Revenue	$ 143,613	$ 154,911	$ 269,138	$ 245,043