CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 25, 2016	Dec. 27, 2015
Accounts receivable, allowances	$ 15,626	$ 13,485
Accumulated depreciation and amortization	$ 893,230	$ 856,974
Common stock, par value (USD per share)	$ 0.1	$ 0.1
Class A Common Stock
Authorized shares (in shares)	300,000,000	300,000,000
Issued shares (in shares)	169,147,029	168,263,533
Treasury shares (in shares)	8,870,801	7,691,129
Class B Common Stock
Authorized shares (in shares)	816,632	816,635
Issued shares (in shares)	816,632	816,635
Treasury shares (in shares)	0	0