CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 25, 2017	Dec. 25, 2016
Accounts receivable, allowances	$ 15,663	$ 16,815
Accumulated depreciation and amortization	$ 931,996	$ 903,736
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)	170,035,282	169,206,879
Treasury shares (in shares)	8,870,801	8,870,801
Class B Common Stock
Authorized shares (in shares)	810,957	816,632
Issued shares (in shares)	810,957	816,632
Treasury shares (in shares)	0	0