Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 24, 2016
OPERATING ACTIVITIES
Net income	$ 112,313	$ 97,776
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of operating property and intangible assets	29,961	26,109
Non-cash interest charges	189	175
Provisions for losses on trade and other accounts receivable	5,643	4,076
Gains on sales/disposals of operating property	(900)	(3,221)
Deferred income taxes, net	(708)	8,925
Stock-based compensation	3,660	2,718
Changes in operating assets and liabilities:
(Increase) decrease in trade and other accounts receivable	(89,504)	50,957
(Increase) decrease in other assets	(8,671)	3,820
Increase (decrease) in accounts payable	53,290	(25,074)
Increase (decrease) in other liabilities	12,980	(5,436)
Increase in insurance claims	14,011	10,472
NET CASH PROVIDED BY OPERATING ACTIVITIES	132,264	171,297
INVESTING ACTIVITIES
Sales and maturities of investments	42,917	30,580
Purchases of investments	(44,423)	(31,938)
Purchases of operating property	(8,800)	(17,833)
Proceeds from sales of operating property	3,594	8,622
Consideration paid for acquisitions	(8,199)
NET CASH USED BY INVESTING ACTIVITIES	(14,911)	(10,569)
FINANCING ACTIVITIES
Decrease in cash overdraft	(2,398)	(7,884)
Dividends paid	(11,739)	(10,572)
Payment for debt issue costs		(1,048)
Proceeds from exercises of stock options	2,531	1,440
Taxes paid in lieu of shares issued related to stock-based compensation plans	(371)	(1,715)
Excess tax benefits from stock-based awards		343
Purchases of common stock		(50,516)
Principal payments on capital lease obligations	(35,662)	(35,147)
NET CASH USED BY FINANCING ACTIVITIES	(47,639)	(105,099)
Effect of exchange rate changes on cash and cash equivalents	1,130	656
Increase in cash and cash equivalents	70,844	56,285
Cash and cash equivalents at beginning of period	178,897	114,520
Cash and cash equivalents at end of period	$ 249,741	$ 170,805