Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash Flows from Operating Activities:
Net income	$ 228,669	$ 210,527
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation & amortization	113,134	110,798
Stock-based compensation expense	19,700	15,348
Gain on sale of assets and businesses	(703)	0
Changes in assets & liabilities, net of effects from acquisitions and dispositions:
Accounts receivable	(72,526)	(5,362)
Accrued interest	(6,209)	(6,123)
Accrued and deferred income taxes	61,674	102,269
Other working capital accounts	59,032	66,877
Other assets and deferred charges	(5,438)	(7,654)
Other	(37,642)	(229)
Accrued insurance expense, net of commercial premiums paid	23,125	22,007
Payments made in settlement of self-insurance claims	(18,765)	(25,349)
Net cash provided by operating activities	364,051	483,109
Cash Flows from Investing Activities:
Property and equipment additions, net of disposals	(189,041)	(144,338)
Acquisition of property and businesses	(20,931)	(17,832)
Proceeds received from sales of assets and businesses	839	0
Costs incurred for purchase and implementation of information technology application	(8,570)	(9,456)
Decrease (increase) in capital reserves of commercial insurance subsidiary	100	(3,000)
Investment in, and advances to, joint venture	(8,675)	0
Net cash used in investing activities	(226,278)	(174,626)
Cash Flows from Financing Activities:
Reduction of long-term debt	(140,676)	(260,633)
Additional borrowings	20,500	21,600
Repurchase of common shares	(9,441)	(29,167)
Dividends paid	(9,422)	(9,662)
Issuance of common stock	2,545	2,540
Profit distributions to noncontrolling interests	(4,217)	(4,118)
Net cash used in financing activities	(140,711)	(279,440)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	1,857	285
(Decrease) increase in cash, cash equivalents and restricted cash	(1,081)	29,328
Cash, cash equivalents and restricted cash, beginning of period	167,297	121,950
Cash, cash equivalents and restricted cash, end of period	166,216	151,278
Supplemental Disclosures of Cash Flow Information:
Interest paid	41,539	39,404
Income taxes paid, net of refunds	2,749	5,253
Noncash purchases of property and equipment	$ 84,708	$ 56,427