Update to Significant Accounting Policies - Schedule rollforward of the allowance for credit losses for accounts receivable, notes receivable and other assets (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 28, 2020	Jun. 30, 2019	Dec. 30, 2019	Dec. 29, 2019
Credit Losses
Retained earnings	$ 212,104			$ 205,697
Income tax receivable	755			$ 4,024
Allowance for Credit Loss
Current period provision for expected credit losses	1,051	$ 676
Accounts Receivable
Allowance for Credit Loss
Balance at beginning of period	7,341
Balance at beginning of period, adjusted			$ 8,253
Current period provision for expected credit losses	833
Write-offs charged against the allowance	(431)
Balance at end of period	8,655
Notes Receivable
Allowance for Credit Loss
Balance at beginning of period	3,572
Balance at beginning of period, adjusted			4,035
Current period provision for expected credit losses	74
Write-offs charged against the allowance	(10)
Recoveries collected	(56)
Transfers	1,054
Balance at end of period	5,097
Interest Receivable
Allowance for Credit Loss
Balance at beginning of period	910
Balance at beginning of period, adjusted			910
Current period provision for expected credit losses	144
Transfers	(1,054)
ASU 2016-13 | Total Adjustments
Credit Losses
Retained earnings			1,100
Income tax receivable			$ 300
ASU 2016-13 | Total Adjustments | Accounts Receivable
Allowance for Credit Loss
Balance at beginning of period	912
ASU 2016-13 | Total Adjustments | Notes Receivable
Allowance for Credit Loss
Balance at beginning of period	$ 463