Commitments And Contingencies (Narrative) (Details) - USD ($)		12 Months Ended
	Oct. 01, 2020	Dec. 31, 2020
James J. Cotter, Jr., Derivative Litigation [Member]
Commitments And Contingencies [Line Items]
Damages sought	$ 809,000
Employment Litigation [Member]
Commitments And Contingencies [Line Items]
Insurance deductible		$ 150,000
Class B [Member] | Cotter Estate [Member] | Cotter, Jr. Related Litigation Matters [Member]
Commitments And Contingencies [Line Items]
Shares held by estate		427,808
Voting stock percent		25.50%
Class B [Member] | Cotter Trust [Member] | Cotter, Jr. Related Litigation Matters [Member]
Commitments And Contingencies [Line Items]
Shares held by estate		696,080
Voting stock percent		41.40%
Class B [Member] | Cotter Voting Trust [Member] | Cotter, Jr. Related Litigation Matters [Member]
Commitments And Contingencies [Line Items]
Shares held by estate		1,123,888
Voting stock percent		66.90%