Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows from Operating Activities:
Net income	$ 797,883	$ 771,312	$ 747,171
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation & amortization	453,076	447,883	416,608
Gains on sales of assets and businesses, net of losses	(2,513)	0	0
Stock-based compensation expense	66,581	56,738	48,109
Costs related to extinguishment of debt	2,727	0	0
Provision for intangible asset impairment	49,310	0	0
Changes in assets & liabilities, net of effects from acquisitions and dispositions:
Accounts receivable	(42,239)	(24,719)	(87,881)
Accrued interest	(4,478)	705	9,766
Accrued and deferred income taxes	(54,052)	(6,405)	22,068
Other working capital accounts	24,696	(15,165)	74,489
Other assets and deferred charges	(31,429)	(27,936)	(25,522)
Other	64,615	(42,564)	81,139
Excess income tax benefits related to stock-based compensation	0	0	45,219
Accrued insurance expense, net of commercial premiums paid	92,863	102,595	84,638
Payments made in settlement of self-insurance claims	(76,147)	(79,192)	(81,962)
Net cash provided by operating activities	1,340,893	1,183,252	1,333,842
Cash Flows from Investing Activities:
Property and equipment additions, net of disposals	(664,962)	(557,506)	(519,939)
Acquisition of property and businesses	(110,464)	(22,878)	(613,803)
Proceeds received from sales of assets and businesses	13,502	108	0
Costs incurred for purchase and implementation of information technology applications	(36,243)	(29,047)	(21,475)
Decrease (Increase) in capital reserves of commercial insurance subsidiary	100	(3,100)	0
Investment in and advances to joint venture	(15,331)	(7,976)	0
Net cash used in investing activities	(813,398)	(620,399)	(1,155,217)
Cash Flows from Financing Activities:
Reduction of long-term debt	(830,496)	(143,106)	(459,183)
Additional borrowings	791,247	41,100	1,170,800
Acquisition of noncontrolling interests in majority owned businesses	0	0	(418,000)
Financing costs	(13,787)	(76)	(12,449)
Repurchase of common shares	(397,425)	(364,401)	(353,380)
Dividends paid	(37,342)	(38,211)	(38,875)
Issuance of common stock	10,196	10,254	9,503
Profit distributions to noncontrolling interests	(14,595)	(24,713)	(69,583)
Net cash used in financing activities	(492,202)	(519,153)	(171,167)
Effect of exchange rate changes on cash and cash equivalents	(2,905)	1,647	(2,790)
Increase in cash and cash equivalents	32,388	45,347	4,668
Cash, cash equivalents and restricted cash, beginning of period	167,297	121,950	117,282
Cash, cash equivalents and restricted cash, end of period	199,685	167,297	121,950
Supplemental Disclosures of Cash Flow Information:
Interest paid	150,293	135,533	107,079
Income taxes paid, net of refunds	293,837	370,855	344,611
Noncash purchases of property and equipment	$ 77,674	$ 82,496	$ 65,702