$ 332,194

$ 289,796

$ 393,222

$ 303,429

$ 355,972

$ 245,346

$ 308,530

$ 260,178

$ 291,750

$ 227,401

$ 252,613

$ 199,427

$ 1,318,641

$ 1,170,026

$ 971,191

804,024

749,515

624,417

431,781

420,160

394,397

372,243

329,355

230,020

$ 514,617

$ 420,511

$ 346,774

Revenue (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
Revenue (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue	$ 332,194	$ 289,796	$ 393,222	$ 303,429	$ 355,972	$ 245,346	$ 308,530	$ 260,178	$ 291,750	$ 227,401	$ 252,613	$ 199,427	$ 1,318,641	$ 1,170,026	$ 971,191
Service Revenue [Member]
Revenue													804,024	749,515	624,417
Commission Revenue [Member]
Revenue													431,781	420,160	394,397
Fees Revenue [Member]
Revenue													372,243	329,355	230,020
Inventory Sales Revenue [Member]
Revenue													$ 514,617	$ 420,511	$ 346,774