Condensed, Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income	[1]	$ 47,722	$ 39,553
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		21,289	19,797
Amortization of debt issue costs		433	434
Provision for uncollectible accounts		851	1,183
Net loss on sale or disposal of assets		563	335
Share-based compensation		4,906	4,132
Excess tax benefits from stock based compensation		(445)	(791)
Other		4,489	(989)
Changes in operating assets and liabilities:
Trade accounts receivable		(3,339)	(14,570)
Inventory, prepaid expenses and other assets		(7,569)	2,862
Accounts payable and other accrued liabilities		(4,801)	(6,954)
Accrued payroll and related liabilities		12,955	14,052
Income taxes		16,855	21,581
Net cash provided by operating activities		93,909	80,625
Cash flows from investing activities:
Business acquisitions, net of cash acquired		(160,385)	(33,652)
Property and equipment additions		(25,806)	(16,526)
Proceeds from sale or disposal of assets		12	92
Other		(7,346)	(576)
Net cash used in investing activities		(193,525)	(50,662)
Cash flows from financing activities:
Repayment of long-term obligations		(9,678)	(5,165)
Proceeds from revolving credit facility		90,000	0
Distributions to noncontrolling interest partners		(1,238)	(1,325)
Purchase of noncontrolling interests		(3,730)	(1,483)
Proceeds from issuance of common stock under stock incentive plans		286	404
Excess tax benefits from stock based compensation		445	791
Stock repurchases		(843)	(44,845)
Other		(333)	(80)
Net cash provided by (used in) financing activities		74,909	(51,703)
Effect of currency exchange rate changes on cash and cash equivalents		299	(365)
Decrease in cash and cash equivalents		(24,408)	(22,105)
Cash and cash equivalents at beginning of period		98,888	81,383
Cash and cash equivalents at end of period		74,480	59,278
Supplemental disclosures of cash flow information:
Interest paid		5,173	4,482
Income taxes paid		$ 14,213	$ 3,077

[1] Includes approximately $1.0 million and $0.8 million of net income related to redeemable and mandatorily redeemable noncontrolling interests for the three months ended March 31, 2016 and 2015, respectively.