CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock Voting Common	Common Stock Nonvoting Common	Preferred Stock	Additional Paid-In Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment
Beginning balance (in shares) at Dec. 29, 2018			67,435,288	1,038,413	1
Beginning balance at Dec. 29, 2018	$ 299,951	$ 169	$ 67	$ 1	$ 0	$ 287,457	$ 12,426	$ 169
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise and vest of share-based awards (in shares)			42,438
Exercise and vesting of share-based awards	0		$ 0			0
Share-based compensation expense	211					211
Dividends paid	(254)						(254)
Net income (loss)	3,774						3,774
Comprehensive income (loss)	3,774						3,774
Ending balance (in shares) at Mar. 30, 2019			67,477,726	1,038,413	1
Ending balance at Mar. 30, 2019	303,851		$ 67	$ 1	$ 0	287,668	16,115
Beginning balance (in shares) at Dec. 29, 2018			67,435,288	1,038,413	1
Beginning balance at Dec. 29, 2018	299,951	169	$ 67	$ 1	$ 0	287,457	12,426	169
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	5,587
Comprehensive income (loss)	5,587
Ending balance (in shares) at Sep. 28, 2019			88,372,134	0	0
Ending balance at Sep. 28, 2019	730,878		$ 88	$ 0	$ 0	712,987	17,803
Beginning balance (in shares) at Mar. 30, 2019			67,477,726	1,038,413	1
Beginning balance at Mar. 30, 2019	303,851		$ 67	$ 1	$ 0	287,668	16,115
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise and vest of share-based awards (in shares)				30,000
Exercise and vesting of share-based awards	314					314
Issuance of common stock upon initial public offering, net of issuance costs (in shares)			19,765,625
Issuance of common stock upon initial public offering, net of issuance costs	400,488		$ 20			400,468
Conversion of nonvoting to voting common shares (in shares)			1,068,413	(1,068,413)
Conversion of nonvoting to voting common shares	0		$ 1	$ (1)
Redemption of preferred shares (in shares)					(1)
Share-based compensation expense	22,750					22,750
Dividends paid	(83)						(83)
Net income (loss)	(10,632)						(10,632)
Comprehensive income (loss)	(10,632)						(10,632)
Ending balance (in shares) at Jun. 29, 2019			88,311,764	0	0
Ending balance at Jun. 29, 2019	716,688		$ 88	$ 0	$ 0	711,200	5,400
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise and vest of share-based awards (in shares)			60,370
Exercise and vesting of share-based awards	(1,021)		$ 0			(1,021)
Deferred offering costs	(84)					(84)
Share-based compensation expense	2,892					2,892
Dividends paid	(42)						(42)
Net income (loss)	12,445						12,445
Comprehensive income (loss)	12,445						12,445
Ending balance (in shares) at Sep. 28, 2019			88,372,134	0	0
Ending balance at Sep. 28, 2019	730,878		$ 88	$ 0	$ 0	712,987	17,803
Beginning balance (in shares) at Dec. 28, 2019			89,005,062	0	0
Beginning balance at Dec. 28, 2019	745,384	439	$ 89	$ 0	$ 0	717,282	28,013	439
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise and vest of share-based awards (in shares)			902,132
Exercise and vesting of share-based awards	6,033		$ 1			6,032
Share-based compensation expense	20,277					20,277
Dividends paid	(147)					(147)
Net income (loss)	12,642						12,642
Comprehensive income (loss)	12,642						12,642
Ending balance (in shares) at Mar. 28, 2020			89,907,194	0	0
Ending balance at Mar. 28, 2020	784,628		$ 90	$ 0	$ 0	743,444	41,094
Beginning balance (in shares) at Dec. 28, 2019			89,005,062	0	0
Beginning balance at Dec. 28, 2019	745,384	$ 439	$ 89	$ 0	$ 0	717,282	28,013	$ 439
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	82,449
Comprehensive income (loss)	82,449
Ending balance (in shares) at Sep. 26, 2020			93,904,922	0	0
Ending balance at Sep. 26, 2020	888,826		$ 94	$ 0	$ 0	777,831	110,901
Beginning balance (in shares) at Mar. 28, 2020			89,907,194	0	0
Beginning balance at Mar. 28, 2020	784,628		$ 90	$ 0	$ 0	743,444	41,094
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise and vest of share-based awards (in shares)			1,511,079
Exercise and vesting of share-based awards	9,845		$ 1			9,844
Tax paid on behalf of employees related to net settlement of share-based awards	(483)					(483)
Share-based compensation expense	10,175					10,175
Dividends paid	(97)					(97)
Net income (loss)	29,333						29,333
Comprehensive income (loss)	29,333						29,333
Ending balance (in shares) at Jun. 27, 2020			91,418,273	0	0
Ending balance at Jun. 27, 2020	833,401		$ 91	$ 0	$ 0	762,883	70,427
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise and vest of share-based awards (in shares)			2,486,649
Exercise and vesting of share-based awards	11,255		$ 3			11,252
Share-based compensation expense	3,857					3,857
Dividends paid	(161)					(161)
Net income (loss)	40,474						40,474
Comprehensive income (loss)	40,474						40,474
Ending balance (in shares) at Sep. 26, 2020			93,904,922	0	0
Ending balance at Sep. 26, 2020	$ 888,826		$ 94	$ 0	$ 0	$ 777,831	$ 110,901