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Earnings Per Share - Schedule of Basic to Diluted Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Reconciliation of basic to diluted loss per share
Net income attributable to Summit Inc.	$ (19,163)	$ 71,289	$ 35,509	$ (53,729)	$ 43,010	$ 81,264	$ 50,000	$ (52,444)	$ 33,906	$ 121,830	$ 36,783
Weighted average shares of Class A stock outstanding (in shares)											70,355,042
Basic income per share (USD per share)	$ (0.17)	$ 0.64	$ 0.32	$ (0.49)	$ 0.39	$ 0.74	$ 0.46	$ (0.49)			$ 0.52
Diluted earnings per share (USD per share)	$ (0.17)	$ 0.64	$ 0.32	$ (0.49)	$ 0.38	$ 0.73	$ 0.46	$ (0.49)
LP Units
Reconciliation of basic to diluted loss per share
Anti dilutive shares excluded from calculation of earnings per share									3,512,669	4,371,705	32,327,907
Common Class A
Reconciliation of basic to diluted loss per share
Weighted average shares of Class A stock outstanding (in shares)									111,380,175	108,696,438	70,355,042
Basic income per share (USD per share)									$ 0.30	$ 1.12	$ 0.52
Add: warrants									25,049	42,035	16,123
Weighted average dilutive shares outstanding (in shares)									112,316,646	109,490,898	70,838,508
Diluted earnings per share (USD per share)									$ 0.30	$ 1.11	$ 0.52
Common Class A \| LP Units
Reconciliation of basic to diluted loss per share
Add: Share-based payment arrangements									0	0	0
Common Class A \| Options
Reconciliation of basic to diluted loss per share
Add: Share-based payment arrangements									282,329	308,355	140,142
Common Class A \| Restricted stock
Reconciliation of basic to diluted loss per share
Add: Share-based payment arrangements									459,280	308,221	240,633
Common Class A \| Performance Stock Units
Reconciliation of basic to diluted loss per share
Add: Share-based payment arrangements									169,813	135,849	86,568