EARNINGS PER SHARE - Schedule of Basic to Diluted Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Apr. 02, 2022	Apr. 03, 2021
Reconciliation of basic to diluted loss per share
Net loss attributable to Summit Inc.	$ (34,292)	$ (22,517)
Diluted net loss attributable to Summit Inc.	$ (34,292)	$ (22,517)
LP Units
Reconciliation of basic to diluted loss per share
Anti dilutive shares excluded from calculation of earnings per share (in shares)	1,314,006	2,613,209
Add: stock options
Reconciliation of basic to diluted loss per share
Anti dilutive shares excluded from calculation of earnings per share (in shares)	290,944	1,175,135
Warrants
Reconciliation of basic to diluted loss per share
Anti dilutive shares excluded from calculation of earnings per share (in shares)	31,519	43,166
Time-vesting restricted stock units
Reconciliation of basic to diluted loss per share
Anti dilutive shares excluded from calculation of earnings per share (in shares)	1,379,251	1,894,877
Market-based restricted stock units
Reconciliation of basic to diluted loss per share
Anti dilutive shares excluded from calculation of earnings per share (in shares)	416,096	410,357
Common Class A And Restricted Stock
Reconciliation of basic to diluted loss per share
Weighted average shares of Class A stock outstanding (in shares)	118,937,466	115,664,725
Weighted average basic shares outstanding (in shares)	118,937,466	115,664,725
Weighted average shares outstanding (in shares)		115,411,204
Basic loss per share (usd per share)	$ (0.29)	$ (0.19)
Common Class A
Reconciliation of basic to diluted loss per share
Weighted average shares of Class A stock outstanding (in shares)	118,777,341	115,411,204
Weighted average basic shares outstanding (in shares)	118,777,341	115,411,204
Basic loss per share (usd per share)	$ (0.29)	$ (0.19)
Add: warrants (in shares)	0	0
Weighted average dilutive shares outstanding (in shares)	118,937,466	115,411,204
Diluted loss per share (usd per share)	$ (0.29)	$ (0.20)
Common Class A \| LP Units
Reconciliation of basic to diluted loss per share
Add: share-based payment arrangements (in shares)	0	0
Common Class A \| Add: stock options
Reconciliation of basic to diluted loss per share
Add: share-based payment arrangements (in shares)	0	0
Common Class A \| Add: restricted stock units
Reconciliation of basic to diluted loss per share
Add: share-based payment arrangements (in shares)	0	0
Common Class A \| Add: performance stock units
Reconciliation of basic to diluted loss per share
Add: share-based payment arrangements (in shares)	0	0
Restricted Stock
Reconciliation of basic to diluted loss per share
Add: Nonvested restricted stock awards of retirement eligible shares (in shares)	160,125	253,521

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