Condensed, Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net income	$ 72,099	$ 70,561
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	37,363	26,456
Amortization of debt issue costs	642	774
Provision for uncollectible accounts	2,551	2,492
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain	(5,719)	0
Net (gain) loss on sale of assets	635	149
Share-based compensation	7,767	2,531
Deferred income taxes	10,020	10,833
Excess tax benefit from exercise of stock options	(248)	(906)
Other	(528)	(202)
Changes in operating assets and liabilities:
Trade accounts receivable	(6,900)	(7,813)
Inventory, prepaid expense and other assets	(5,795)	(5,222)
Accounts payable and other accrued liabilities	(1,805)	(7,994)
Accrued payroll and related liabilities	1,102	16,021
Income taxes	(2,516)	7,940
Net cash provided by operating activities	108,668	115,620
Cash flows from investing activities:
Business acquisitions, net of cash acquired	(75,828)	(11,804)
Real estate acquired in connection with business acquisitions	0	(1,900)
Property and equipment additions	(37,165)	(28,434)
Proceeds from sale of assets	78	140
Other	55	(493)
Net cash used in investing activities	(112,860)	(42,491)
Cash flows from financing activities:
Repayment of debt	(43,318)	(14,164)
Proceeds from issuance of long-term debt	50,000	0
Proceeds from revolving credit facility	50,000	0
Repayment of revolving credit facility	(50,000)	0
Payment of financing costs	(122)	0
Distributions to noncontrolling interest partners	(1,631)	(1,141)
Proceeds from issuance of common stock under stock option plans	2,885	2,456
Excess tax benefit from exercise of stock options	248	906
Stock repurchases	(2,770)	(2,337)
Other	(656)	(345)
Net cash provided by (used in) financing activities	4,636	(14,625)
Effect of currency exchange rate changes on cash and cash equivalents	(28)	153
Decrease in cash and cash equivalents	416	58,657
Cash and cash equivalents at beginning of period	63,651	97,126
Cash and cash equivalents at end of period	64,067
Supplemental disclosures of cash flow information:
Interest paid	7,788	8,127
Income taxes paid	32,685	25,696
Detail of acquisitions:
Fair value of assets acquired	147,527	11,889
Business Combination, Step Acquisition, Equity Interest in Acquiree, Fair Value	(11,850)
Noncontrolling Interest, Increase from Business Combination	(8,161)	0
Cash paid for acquisitions	(75,328)
CashPaidToDebtHolders	(25,915)	0
Stock Issued During Period, Value, Acquisitions	(10,500)	0
Holdbacks	(1,525)	(500)
Liabilities assumed	$ 14,248	$ (56)