Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017
OPERATING ACTIVITIES
Net income	$ 119,965	$ 69,893
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of operating property and intangible assets	21,766	19,831
Non-cash interest charges	126	127
Provisions for losses on trade and other accounts receivable	4,297	3,601
Gains on sales/disposals of operating property	(988)	(701)
Deferred income taxes, net	5,585	1,766
Stock-based compensation	8,102	2,237
Changes in operating assets and liabilities:
Increase in trade and other accounts receivable	(48,651)	(22,917)
Increase in other assets	(16,537)	(12,658)
Increase in accounts payable	20,161	8,829
(Decrease) increase in other liabilities	(4,488)	3,316
Increase in insurance claims	3,691	6,475
NET CASH PROVIDED BY OPERATING ACTIVITIES	113,029	79,799
INVESTING ACTIVITIES
Sales and maturities of investments	18,399	33,486
Purchases of investments	(19,653)	(34,360)
Purchases of operating property	(4,121)	(6,628)
Proceeds from sales of operating property	2,939	2,793
NET CASH USED BY INVESTING ACTIVITIES	(2,436)	(4,709)
FINANCING ACTIVITIES
Increase (decrease) in cash overdraft	3,123	(2,106)
Dividends paid	(75,481)	(7,544)
Proceeds from exercises of stock options	1,039	1,962
Taxes paid in lieu of shares issued related to stock-based compensation plans	(2,812)	(365)
Purchases of common stock	(105,488)
Principal payments on capital lease obligations	(22,768)	(24,417)
Payment of contingent consideration	(985)
NET CASH USED BY FINANCING ACTIVITIES	(203,372)	(32,470)
Effect of exchange rate changes on cash and cash equivalents	(996)	585
(Decrease) increase in cash and cash equivalents	(93,775)	43,205
Cash and cash equivalents at beginning of period	242,416	178,897
Cash and cash equivalents at end of period	$ 148,641	$ 222,102