Condensed, Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net income	[1]	$ 52,453	$ 47,722
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		30,401	21,289
Amortization of debt issue costs		383	433
Provision for uncollectible accounts		1,794	851
Net loss on sale or disposal of assets		250	563
Share-based compensation		3,962	4,906
Excess tax benefits from share-based compensation		0	(445)
Other		884	4,489
Changes in operating assets and liabilities:
Trade accounts receivable		(1,594)	(3,339)
Inventory, prepaid expenses and other assets		5,507	(7,569)
Accounts payable and other accrued liabilities		3,491	(4,801)
Accrued payroll and related liabilities		(24,748)	12,955
Income taxes		27,508	16,855
Net cash provided by operating activities		100,291	93,909
Cash flows from investing activities:
Business acquisitions, net of cash acquired		(81,721)	(160,385)
Property and equipment additions		(28,919)	(25,806)
Proceeds from sale of assets		349	12
Other		(6,203)	(7,346)
Net cash used in investing activities		(116,494)	(193,525)
Cash flows from financing activities:
Repayment of long-term obligations		(17,813)	(9,678)
Proceeds from revolving credit facility		45,000	90,000
Distributions to noncontrolling interest partners		(1,138)	(1,238)
Proceeds from formation of noncontrolling interests		335	0
Purchase of noncontrolling interests		(1,400)	(3,730)
Proceeds from issuance of common stock under stock incentive plans		90	286
Excess tax benefits from share-based compensation		0	445
Stock repurchases		(95)	(843)
Other		(812)	(333)
Net cash provided by financing activities		24,167	74,909
Effect of currency exchange rate changes on cash and cash equivalents		158	299
Increase (decrease) in cash and cash equivalents		8,122	(24,408)
Cash and cash equivalents at beginning of period		81,409	98,888
Cash and cash equivalents at end of period		89,531	74,480
Supplemental disclosures of cash flow information:
Interest paid		7,875	5,173
Income taxes paid		$ 7,081	$ 14,213

[1] Includes approximately $0.8 million and $1 million of net income related to redeemable and mandatorily redeemable noncontrolling interests for the three months ended March 31, 2017 and 2016, respectively.