Significant Accounting Policies - Schedule rollforward of the allowance for credit losses for accounts receivable, notes receivable and other assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 26, 2021	Sep. 27, 2020
Allowance for Credit Loss
Current period (credit) provision for expected credit losses	$ (920)	$ (334)
Accounts Receivable
Allowance for Credit Losses
Balance at beginning of period	3,622
Current period benefit for expected credit losses	(80)
Write-offs charged against the allowance	(1,212)
Balance at end of period	2,330
Notes Receivable
Allowance for Credit Losses
Balance at beginning of period	3,211
Current period benefit for expected credit losses	(563)
Write-offs charged against the allowance	(843)
Recoveries collected	(277)
Balance at end of period	$ 1,528