Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
OPERATING ACTIVITIES
Net income	$ 137,350	$ 147,689	$ 138,809
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of operating property	35,796	29,102	27,575
Non-cash interest charges	238	218	218
Provisions for losses on trade and other accounts receivable	5,735	5,890	5,315
Gains on sales/disposals of operating property	(3,477)	(216)	(2,143)
Deferred income taxes, net	6,328	6,792	5,434
Stock-based compensation	2,747	6,925	6,797
Changes in operating assets and liabilities:
(Increase) decrease in trade and other accounts receivable	(6,233)	20,713	(60,454)
Decrease (increase) in other assets	9,298	(1,177)	(9,046)
(Decrease) increase in accounts payable	(9,598)	3,632	62,281
Increase (decrease) in other liabilities	288	1,222	(2,468)
Increase (decrease) in insurance claims	11,770	(4,768)	(70,449)
NET CASH PROVIDED BY OPERATING ACTIVITIES	190,242	216,022	101,869
INVESTING ACTIVITIES
Sales and maturities of investments	41,795	38,684	34,701
Purchases of investments	(43,529)	(44,238)	(36,473)
Purchases of operating property	(22,645)	(4,804)	(10,539)
Proceeds from sales of operating property	10,212	1,685	7,465
NET CASH USED BY INVESTING ACTIVITIES	(14,167)	(8,673)	(4,846)
FINANCING ACTIVITIES
Increase in cash overdraft	642	980	6,849
Dividends paid	(14,332)	(57,882)	(27,606)
Payment for debt issue costs	(1,048)
Proceeds from exercises of stock options	2,329	1,459	3,760
Taxes paid in lieu of shares issued related to stock-based compensation plans	(3,043)	(2,225)	(4,041)
Excess tax benefits from stock-based awards	1,386	671	2,500
Purchases of common stock	(50,516)	(161,152)	(56,393)
Principal payments on capital lease obligations	(47,492)	(36,520)	(37,416)
NET CASH USED BY FINANCING ACTIVITIES	(112,074)	(254,669)	(112,347)
Effect of exchange rate changes on cash and cash equivalents	376	(2,104)	(1,034)
Increase (decrease) in cash and cash equivalents	64,377	(49,424)	(16,358)
Cash and cash equivalents at beginning of period	114,520	163,944	180,302
Cash and cash equivalents at end of period	$ 178,897	$ 114,520	$ 163,944