Earnings Per Share - Reconciliation of earnings (Details) - USD ($) $ / shares in Units, $ in Thousands	4 Months Ended		9 Months Ended
	Oct. 07, 2018	Oct. 08, 2017	Oct. 07, 2018	Oct. 08, 2017
Earnings Per Share
Net income	$ 10,160	$ 5,106	$ 9,667	$ 7,642
Weighted average shares outstanding for basic EPS	73,117,389	72,446,404	72,713,906	72,437,033
Effect of dilutive securities:
Assumed exercise of time-based stock options and vesting of restricted stock	1,329,271	1,806,970	1,357,798	3,151,149
Weighted average shares and share equivalents outstanding for diluted EPS	74,446,660	74,253,374	74,071,704	75,588,182
Basic earnings per share (in dollars per share)	$ 0.14	$ 0.07	$ 0.13	$ 0.11
Diluted earnings per share (in dollars per share)	$ 0.14	$ 0.07	$ 0.13	$ 0.10
Potentially dilutive securities excluded from the computation of diluted income per share (in shares)	6,301,675	6,441,045	6,501,271	3,623,034