Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash Flows from Operating Activities:
Net income	$ 210,527	$ 215,719
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation & amortization	110,798	104,049
Stock-based compensation expense	15,348	13,204
Changes in assets & liabilities, net of effects from acquisitions and dispositions:
Accounts receivable	(5,362)	(79,962)
Accrued interest	(6,123)	688
Accrued and deferred income taxes	102,269	91,131
Other working capital accounts	66,877	98,972
Other assets and deferred charges	(7,755)	(5,803)
Other	(229)	20,911
Excess income tax benefits related to stock-based compensation	0	11,002
Accrued insurance expense, net of commercial premiums paid	22,007	22,616
Payments made in settlement of self-insurance claims	(25,349)	(17,298)
Net cash provided by operating activities	483,008	475,229
Cash Flows from Investing Activities:
Property and equipment additions, net of disposals	(144,338)	(127,214)
Acquisition of property and businesses	(17,832)	(19,543)
Increase in capital reserves of commercial insurance subsidiary	(3,000)	0
Costs incurred for purchase and implementation of information technology application	(9,456)	0
Net cash used in investing activities	(174,626)	(146,757)
Cash Flows from Financing Activities:
Reduction of long-term debt	(260,633)	(166,671)
Additional borrowings	21,600	14,400
Financing costs	0	(44)
Repurchase of common shares	(29,167)	(171,042)
Dividends paid	(9,662)	(9,757)
Issuance of common stock	2,540	2,331
Profit distributions to noncontrolling interests	(4,118)	(3,407)
Net cash used in financing activities	(279,440)	(334,190)
Effect of exchange rate changes on cash and cash equivalents	285	(920)
Increase (decrease) in cash and cash equivalents	29,227	(6,638)
Cash and cash equivalents, beginning of period	33,747	61,228
Cash and cash equivalents, end of period	62,974	54,590
Supplemental Disclosures of Cash Flow Information:
Interest paid	39,404	27,133
Income taxes paid, net of refunds	5,253	9,093
Noncash purchases of property and equipment	$ 56,427	$ 47,374