Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 30, 2017
Allowance on trade accounts receivable	$ 6,549	$ 6,131
Allowance on other receivables	6,495	6,012
Accumulated depreciation and amortization on operating property	$ 232,760	$ 218,700
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized shares	160,000,000	160,000,000
Common stock, issued shares	67,847,692	67,740,380
Treasury stock, shares	26,754,810	25,749,493

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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