Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 26, 2017	Dec. 27, 2016
Condensed Consolidated Balance Sheets
Receivables, allowance for doubtful accounts (in dollars)	$ 52	$ 33
Property and equipment, accumulated depreciation (in dollars)	512,061	457,102
Intangible assets, accumulated amortization (in dollars)	$ 12,445	$ 11,753
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	71,101,654	70,619,737
Common stock, shares outstanding	71,101,654	70,619,737