Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash Flows from Operating Activities:
Net income	$ 400,915	$ 411,168
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation & amortization	223,910	205,460
Stock-based compensation expense	29,053	24,693
Changes in assets & liabilities, net of effects from acquisitions and dispositions:
Accounts receivable	941	(45,729)
Accrued interest	211	9,158
Accrued and deferred income taxes	(5,529)	17,997
Other working capital accounts	(93,715)	123,315
Other assets and deferred charges	(19,927)	(8,149)
Other	(23,411)	52,050
Excess income tax benefits related to stock-based compensation	0	35,247
Accrued insurance expense, net of commercial premiums paid	58,903	44,231
Payments made in settlement of self-insurance claims	(37,759)	(33,012)
Net cash provided by operating activities	533,592	836,429
Cash Flows from Investing Activities:
Property and equipment additions, net of disposals	(262,452)	(247,715)
Acquisition of property and businesses	(19,610)	(27,525)
Increase in capital reserves of commercial insurance subsidiary	(3,000)	0
Costs incurred for purchase and implementation of information technology application	(19,448)	0
Net cash used in investing activities	(304,510)	(275,240)
Cash Flows from Financing Activities:
Reduction of long-term debt	(45,675)	(843,351)
Additional borrowings	21,600	1,022,239
Acquisition of noncontrolling interests in majority owned businesses	0	(418,000)
Financing costs	0	(10,734)
Repurchase of common shares	(147,463)	(239,139)
Dividends paid	(19,280)	(19,484)
Issuance of common stock	4,927	4,362
Profit distributions to noncontrolling interests	(11,430)	(59,615)
Net cash used in financing activities	(197,321)	(563,722)
Effect of exchange rate changes on cash and cash equivalents	938	(2,422)
Increase (decrease) in cash and cash equivalents	32,699	(4,955)
Cash and cash equivalents, beginning of period	33,747	61,228
Cash and cash equivalents, end of period	66,446	56,273
Supplemental Disclosures of Cash Flow Information:
Interest paid	66,765	53,558
Income taxes paid, net of refunds	216,214	165,947
Noncash purchases of property and equipment	$ 63,089	$ 42,747