Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
OPERATING ACTIVITIES
Net income	$ 192,106	$ 227,703	$ 255,213
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of operating property and intangible assets	45,855	44,468	43,570
Non-cash interest charges	334	253	253
Provisions for losses on trade and other accounts receivable	9,415	9,831	7,415
Gains on sales/disposals of operating property	(2,576)	(1,016)	(979)
Impairment of intangible and other assets	2,582
Deferred income taxes, net	1,130	4,767	2,115
Stock-based compensation	4,639	4,236	18,256
Changes in operating assets and liabilities:
(Increase) decrease in trade and other accounts receivable	(285,169)	81,415	(57,419)
Increase in other assets	(4,719)	(11,395)	(2,962)
Increase (decrease) in accounts payable	108,090	(42,138)	22,527
Increase (decrease) in other liabilities	28,496	(17,786)	8,367
Increase in insurance claims	110,534	7,502	1,545
NET CASH PROVIDED BY OPERATING ACTIVITIES	210,717	307,840	297,901
INVESTING ACTIVITIES
Net change in other short-term investments	131	(131)
Sales and maturities of investments	22,632	62,922	51,576
Purchases of investments	(25,550)	(65,922)	(54,041)
Purchases of operating property	(30,626)	(19,416)	(9,747)
Proceeds from sales of operating property	7,760	3,991	4,018
Consideration paid for acquisition	(2,766)
NET CASH USED BY INVESTING ACTIVITIES	(28,419)	(18,556)	(8,194)
FINANCING ACTIVITIES
Increase (decrease) in cash overdraft	20,870	(1,461)	13,097
Dividends paid	(109,504)	(27,891)	(88,918)
Payment for debt issue costs	(1,132)
Proceeds from exercises of stock options	725	1,056	1,435
Taxes paid in lieu of shares issued related to stock-based compensation plans	(3,326)	(8,456)	(3,938)
Purchases of common stock	(115,962)	(88,578)	(208,087)
Principal payments on finance lease obligations	(43,703)	(44,635)	(43,283)
Purchase of noncontrolling interest		(600)
Payment of contingent consideration			(985)
NET CASH USED BY FINANCING ACTIVITIES	(252,032)	(170,565)	(330,679)
Effect of exchange rate changes on cash and cash equivalents	(427)	1,060	(1,708)
(Decrease) increase in cash and cash equivalents	(70,161)	119,779	(42,680)
Cash and cash equivalents at beginning of period	319,515	199,736	242,416
Cash and cash equivalents at end of period	$ 249,354	$ 319,515	$ 199,736