Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 27, 2021	Dec. 26, 2020
Allowance on trade accounts receivable	$ 7,095	$ 8,670
Allowance on other receivables	6,711	7,239
Accumulated depreciation and amortization on operating property	$ 309,464	$ 299,407
Common stock, par value	$ 0.01	$ 0.01
Common stock, authorized shares	160,000,000	160,000,000
Common stock, issued shares	68,212,296	68,183,702
Treasury stock, shares	29,803,726	29,797,639

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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The valuation allowance as of the balance sheet date to reduce the gross amount of receivables to estimated net realizable value, which would be presented in parentheses on the face of the balance sheet.

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