Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Jun. 27, 2018	Dec. 27, 2017
Assets [Abstract]
Accumulated depreciation	$ 245,733	$ 243,325
Shareholders' equity (deficit)
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	135,000	135,000
Common stock, shares issued	108,470	107,740
Common stock, shares outstanding	63,456	64,589
Treasury stock, at cost, shares	45,014	43,151