Consolidated Balance Sheets (Unaudited) Parenthetical - USD ($) $ in Thousands	Jun. 26, 2016	Dec. 27, 2015	Jun. 28, 2015
Current assets
Accounts receivable, allowance for doubtful accounts	$ 32,800	$ 14,900	$ 16,300
Property, plant and equipment, accumulated depreciation	375,300	363,600	359,300
Other assets
Other intangibles, accumulated amortization	$ 858,700	$ 841,300	$ 823,800
Shareholders' equity
Preference stock, par value (in dollars per share)	$ 2.5	$ 2.5	$ 2.5
Preference stock, authorized shares (in shares)	5,000,000	5,000,000	5,000,000
Preference stock, issued (in shares)	0	0	0
Common stock, par value (in dollars per share)	$ 0.5	$ 0.5	$ 0.5
Common stock, authorized shares (in shares)	600,000,000	600,000,000	600,000,000
Common stock, issued (in shares)	209,694,630	209,694,630	209,694,630
Treasury stock, at cost; shares (in shares)	84,241,018	84,899,200	84,781,723