Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
OPERATING ACTIVITIES
Net income	$ 176,996	$ 137,350	$ 147,689
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of operating property and intangible assets	40,560	35,796	29,102
Non-cash interest charges	253	238	218
Provisions for losses on trade and other accounts receivable	7,439	5,735	5,890
Gains on sales/disposals of operating property	(774)	(3,477)	(216)
Deferred income taxes, net	(17,031)	6,328	6,792
Stock-based compensation	7,721	2,747	6,925
Changes in operating assets and liabilities:
(Increase) decrease in trade and other accounts receivable	(181,235)	(6,233)	20,713
(Increase) decrease in other assets	(1,966)	9,298	(1,177)
Increase (decrease) in accounts payable	68,859	(9,598)	3,632
Increase in other liabilities	22,085	288	1,222
Increase (decrease) in insurance claims	16,056	11,770	(4,768)
NET CASH PROVIDED BY OPERATING ACTIVITIES	138,963	190,242	216,022
INVESTING ACTIVITIES
Sales and maturities of investments	56,442	41,795	38,684
Purchases of investments	(58,504)	(43,529)	(44,238)
Purchases of operating property	(15,586)	(22,645)	(4,804)
Proceeds from sales of operating property	4,032	10,212	1,685
Consideration paid for acquisitions	(8,460)
NET CASH USED BY INVESTING ACTIVITIES	(22,076)	(14,167)	(8,673)
FINANCING ACTIVITIES
Increase in cash overdraft	5,991	642	980
Dividends paid	(15,938)	(14,332)	(57,882)
Payment for debt issue costs		(1,048)
Proceeds from exercises of stock options	3,183	2,329	1,459
Taxes paid in lieu of shares issued related to stock-based compensation plans	(881)	(3,043)	(2,225)
Excess tax benefits from stock-based awards		1,386	671
Purchases of common stock	0	(50,516)	(161,152)
Principal payments on capital lease obligations	(46,751)	(47,492)	(36,520)
NET CASH USED BY FINANCING ACTIVITIES	(54,396)	(112,074)	(254,669)
Effect of exchange rate changes on cash and cash equivalents	1,028	376	(2,104)
Increase (decrease) in cash and cash equivalents	63,519	64,377	(49,424)
Cash and cash equivalents at beginning of period	178,897	114,520	163,944
Cash and cash equivalents at end of period	$ 242,416	$ 178,897	$ 114,520