Cash and Receivables Allowance for Doubtful Accounts Receivable (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 27, 2020	Sep. 29, 2019
Allowance for Doubtful Accounts
Balance at beginning of period; accounts receivable	$ 3,314	$ 4,940
Provision for doubtful accounts; accounts receivable	699	(1,544)
Uncollectible accounts written off, net of recoveries; accounts receivable	(93)	(220)
Balance at end of period; accounts receivable	3,920	3,176
Balance at beginning of period; notes receivable	6,705	2,000
Provision for doubtful accounts; notes receivable	(8)	2,089
Uncollectible accounts written off, net of recoveries; notes receivable	(1,192)	11
Balance at end of period; notes receivable	5,505	4,100
Balance at beginning of period; total	10,019	6,940
Provision for doubtful accounts; total	691	545
Uncollectible accounts written off, net of recoveries; total	(1,285)	(209)
Balance at end of period; total	$ 9,425	$ 7,276