Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Period to settle advances against auction contracts	14 days
Advertising expense	$ 9.4	$ 9.9	$ 8.8
Selling, general and administrative expenses
Disaggregation of Revenue [Line Items]
Advertising expense	$ 26.1	$ 16.7	$ 14.1
Maximum
Disaggregation of Revenue [Line Items]
Registration fee term	2 years
Minimum
Disaggregation of Revenue [Line Items]
Registration fee term	1 year