Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net income	$ 263,846	$ 138,907
Adjustments to reconcile net income to net cash provided by operating activities:
Loss on disposal of assets and impairments	10,090	128,608
Depreciation	275,634	258,067
Amortization of intangibles	52,573	50,272
Foreign currency transaction loss	190	1,638
Deferred income taxes, net of acquisitions	26,399	(10,378)
Amortization of debt issuance costs	2,081	2,101
Share-based compensation	20,262	23,364
Interest income on restricted investments	(126)	(283)
Interest accretion	7,403	6,887
Adjustments to contingent consideration	349	11,013
Payment of contingent consideration recorded in earnings	(11)
Net change in operating assets and liabilities, net of acquisitions	6,241	(58,290)
Net cash provided by operating activities	664,931	551,906
Cash flows from investing activities:
Payments for acquisitions, net of cash acquired	(485,519)	(347,936)
Capital expenditures for property and equipment	(201,712)	(202,617)
Proceeds from disposal of assets	2,074	20,617
Change in restricted investments, net of interest income		(768)
Other	(77)	(1,732)
Net cash used in investing activities	(685,234)	(532,436)
Cash flows from financing activities:
Proceeds from long-term debt	165,736	864,952
Principal payments on notes payable and long-term debt	(338,137)	(585,762)
Payment of contingent consideration recorded at acquisition date	(4,976)	(5,565)
Change in book overdraft	(1,132)	19,479
Proceeds from option and warrant exercises		1,946
Payments for repurchase of common shares	(42,040)
Payments for cash dividends	(73,584)	(63,463)
Tax withholdings related to net share settlements of equity-based compensation	(14,589)	(13,621)
Debt issuance costs	(2,757)	(3,519)
Proceeds from sale of common shares held in trust	2,146	7,735
Other	(103)	(1,094)
Net cash provided by (used in) financing activities	(309,436)	221,088
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(915)	672
Net increase (decrease) in cash, cash equivalents and restricted cash	(330,654)	241,230
Cash, cash equivalents and restricted cash at beginning of period	556,467	169,112
Plus (less): change in cash held for sale	33	(305)
Cash, cash equivalents and restricted cash at end of period	225,846	410,037
Non-cash financing activities:
Liabilities assumed and notes payable issued to sellers of businesses acquired	$ 99,390	136,090
Non-cash consideration received for asset sales		$ 12,632