Condensed, Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net income	[1]	$ 122,877	$ 114,148
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		60,920	46,978
Amortization of debt issue costs		767	865
Provision for uncollectible accounts		4,319	2,891
Debt retirement costs		0	(1,600)
Net loss on sale or disposal of assets		480	292
Share-based compensation		7,993	9,104
Excess tax benefits from share-based compensation		0	(1,421)
Other		(1,332)	6,665
Changes in operating assets and liabilities:
Trade accounts receivable		(5,318)	(7,065)
Inventory, prepaid expenses and other assets		1,287	(15,607)
Accounts payable and other accrued liabilities		8,777	5,889
Accrued payroll and related liabilities		(1,936)	2,817
Income taxes		16,449	23,557
Net cash provided by operating activities		215,283	190,713
Cash flows from investing activities:
Business acquisitions, net of cash acquired		(123,852)	(540,878)
Property and equipment additions		(54,638)	(58,814)
Proceeds from sale of assets		1,747	282
Other		(7,900)	(4,924)
Net cash used in investing activities		(184,643)	(604,334)
Cash flows from financing activities:
Repayment of long-term obligations		(28,259)	(1,256,250)
Proceeds from issuance of long-term obligations		0	1,255,000
Repayment of revolving credit facility		(30,000)	0
Proceeds from revolving credit facility		70,000	435,000
Payment of financing costs		0	(3,829)
Distributions to noncontrolling interest partners		(2,333)	(2,554)
Purchase of noncontrolling interests		(1,401)	(3,730)
Proceeds from formation of noncontrolling interests		335	0
Proceeds from issuance of common stock under stock incentive plans		90	1,122
Excess tax benefits from share-based compensation		0	1,421
Stock repurchases		(129)	(843)
Other		(1,479)	(1,233)
Net cash provided by financing activities		6,824	424,104
Effect of currency exchange rate changes on cash and cash equivalents		179	313
Increase in cash and cash equivalents		37,643	10,796
Cash and cash equivalents at beginning of period		81,409	98,888
Cash and cash equivalents at end of period		119,052	109,684
Supplemental disclosures of cash flow information:
Interest paid		15,990	12,272
Income taxes paid		$ 62,727	$ 47,326

[1] Includes approximately $1.8 million and $2.1 million of net income related to redeemable and mandatorily redeemable noncontrolling interests for the six months ended June 30, 2017 and 2016, respectively.