Selected Quarterly Financial and Earnings Data (Unaudited) Quarterly Table (Details) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Jan. 03, 2016 USD ($) $ / shares	Sep. 27, 2015 USD ($) $ / shares	Jun. 28, 2015 USD ($) $ / shares	Mar. 29, 2015 USD ($) $ / shares	Dec. 28, 2014 USD ($) $ / shares	Sep. 28, 2014 USD ($) $ / shares	Jun. 29, 2014 USD ($) $ / shares	Mar. 30, 2014 USD ($) $ / shares	Jan. 03, 2016 USD ($) $ / shares	Dec. 28, 2014 USD ($) $ / shares	Dec. 29, 2013 USD ($) $ / shares
Quarterly Financial Information Disclosure [Abstract]
Restaurant sales	$ 229,056	$ 217,676	$ 219,102	$ 193,170	$ 192,897	$ 179,822	$ 168,583	$ 151,453	$ 859,004	$ 692,755	$ 663,483
Operating income (loss)	11,561	11,751	12,358	(4,462)	(2,994)	330	1,597	(6,484)	31,208	(7,551)	(5,075)
Net income (loss)	$ 7,018	$ 7,239	$ (4,977)	$ (9,276)	$ (27,035)	$ (1,721)	$ (1,932)	$ (7,429)	$ 4	$ (38,117)	$ (13,519)
Basic and diluted net income (loss) per share | $ / shares	$ 0.16	$ 0.16	$ (0.14)	$ (0.27)	$ (0.78)	$ (0.05)	$ (0.06)	$ (0.32)	$ 0.00	$ (1.23)	$ (0.59)
Restaurants at end of period	705	660	657	659	674	581	560	560	705	674