Net Income per Share Schedule of reconciliation of earnings per share (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 29, 2017	Sep. 29, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 30, 2016	Sep. 23, 2016	Jun. 24, 2016	Mar. 25, 2016	Dec. 29, 2017	Dec. 30, 2016	Dec. 25, 2015
Net Income (Loss) Available to Common Stockholders, Basic [Abstract]
Net income	$ 9,483	$ 2,851	$ 3,674	$ (1,642)	$ 9,142	$ 1,343	$ (8,455)	$ 993	$ 14,366	$ 3,023	$ 16,209
Net Income (Loss) Available to Common Stockholders, Diluted [Abstract]
Interest on convertible notes, net of tax									536	0	403
Adjusted net income									$ 14,902	$ 3,023	$ 16,612
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Weighted average basic common shares outstanding (in shares)									26,118,482	25,919,480	25,532,172
Dilutive effect of unvested common shares (in shares)									68,670	110,129	79,385
Dilutive effect of convertible notes (in shares)									1,237,374	0	897,437
Weighted average diluted common shares outstanding (in shares)									27,424,526	26,029,609	26,508,994