Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue	$ 331,542	$ 289,796	$ 993,847	$ 986,447
Service Revenue [Member]
Revenue	222,679	178,577	639,941	585,555
Commission Revenue [Member]
Revenue	112,762	90,928	331,711	317,674
Fees Revenue [Member]
Revenue	109,917	87,649	308,230	267,881
Inventory Sales Revenue [Member]
Revenue	$ 108,863	$ 111,219	$ 353,906	$ 400,892