Revenue Recognition (Details)	6 Months Ended
	Jun. 28, 2020	Jun. 27, 2021
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Seller and Buyer Performance Obligations		90.00%
Auction Access, Term	1 year
Auction Sales | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-07
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation satisfaction		1 year
Registration Fee Revenue | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-07
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation satisfaction		1 year