Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 30, 2020
Assets
Accumulated depreciation	$ 146,825	$ 146,583
Accumulated amortization	$ 10,333	$ 9,907
Shareholders' deficit
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	135,000,000	135,000,000
Common stock, shares issued (in shares)	64,145,000	63,962,000
Common stock, shares outstanding (in shares)	64,145,000	63,962,000