Condensed, Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash flows from operating activities:
Net income	$ 107,741	$ 101,920
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	56,882	41,386
Amortization of debt issue costs	961	1,169
Provision for uncollectible accounts	4,437	4,510
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain	(5,719)	0
Debt retirement costs	0	2,764
Net (gain) loss on sale of assets	1,022	(43)
Share-based compensation	10,466	6,610
Deferred income taxes	14,119	14,649
Excess tax benefit from exercise of stock options	(358)	(963)
Other	(838)	(489)
Changes in operating assets and liabilities:
Trade accounts receivable	(5,079)	(7,018)
Inventory, prepaid expense and other assets	(6,727)	(9,806)
Accounts payable and other accrued liabilities	3,161	(8,328)
Accrued payroll and related liabilities	10,007	8,523
Income taxes	(1,636)	8,707
Net cash provided by operating activities	188,439	163,591
Cash flows from investing activities:
Business acquisitions, net of cash acquired	(108,031)	(190,363)
Real estate acquired in connection with business acquisitions	(1,602)	(1,900)
Property and equipment additions	(55,257)	(43,275)
Proceeds from sale of assets	112	447
Other	(1,583)	(723)
Net cash used in investing activities	(166,361)	(235,814)
Cash flows from financing activities:
Repayment of debt	(52,040)	(90,945)
Proceeds from issuance of long-term debt	50,000	150,000
Proceeds from revolving credit facility	50,000	50,000
Repayment of revolving credit facility	(50,000)	(50,000)
Payment of financing costs	(122)	(2,944)
Distributions to noncontrolling interest partners	(2,802)	(1,959)
Proceeds from issuance of common stock under stock option plans	3,322	2,596
Excess tax benefit from exercise of stock options	358	963
Stock repurchases	(3,897)	(2,663)
Other	(1,273)	(345)
Net cash provided by (used in) financing activities	(6,454)	54,703
Effect of currency exchange rate changes on cash and cash equivalents	386	(363)
Decrease in cash and cash equivalents	16,010	(17,883)
Cash and cash equivalents at beginning of period	63,651	97,126
Cash and cash equivalents at end of period	79,661
Supplemental disclosures of cash flow information:
Interest paid	11,614	12,214
Income taxes paid	48,671	40,601
Detail of acquisitions:
Fair value of assets acquired	187,515	241,688
Business Combination, Step Acquisition, Equity Interest in Acquiree, Fair Value	(11,850)	0
Noncontrolling Interest, Increase from Business Combination	(8,161)	0
Cash paid for acquisitions	(108,031)	(189,255)
CashPaidToDebtHolders	(25,915)	(26,048)
Stock Issued During Period, Value, Acquisitions	(10,500)	0
Contingent consideration	(934)	(481)
Holdbacks	(2,525)	(800)
Liabilities assumed	$ 19,599	$ 25,104