Condensed, Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Cash flows from operating activities:
Net income	$ 70,561	$ 63,449
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	26,456	21,706
Amortization of debt issue costs	774	239
Provision for uncollectible accounts	2,492	3,143
Net loss (gain) on sale of assets	149	11
Share-based compensation	2,531	5,855
Deferred income taxes	10,833	6,461
Excess tax benefit from exercise of stock options	(906)	(331)
Other	(202)	(225)
Changes in operating assets and liabilities:
Trade accounts receivable	(7,813)	(7,344)
Inventory, prepaid expense and other assets	(5,222)	(727)
Accounts payable and other accrued liabilities	(7,994)	13,691
Accrued payroll and related liabilities	16,021	12,656
Income taxes	7,940	(7,248)
Net cash provided by operating activities	115,620	111,336
Cash flows from investing activities:
Business acquisitions, net of cash acquired	(11,804)	(20,078)
Real estate acquired in connection with business acquisitions	(1,900)	(1,300)
Property and equipment additions	(28,434)	(27,925)
Proceeds from sale of assets	140	9
Other	(493)	(162)
Net cash used in investing activities	(42,491)	(49,456)
Cash flows from financing activities:
Repayment of debt	(14,164)	(12,859)
Distributions to noncontrolling interest partners	(1,141)	(2,021)
Proceeds from issuance of common stock under stock option plans	2,456	3,770
Excess tax benefit from exercise of stock options	906	331
Stock repurchases	(2,337)	(2,253)
Other	(345)	(266)
Net cash used in financing activities	(14,625)	(13,298)
Effect of currency exchange rate changes on cash and cash equivalents	153	(6)
Increase in cash and cash equivalents	58,657	48,576
Cash and cash equivalents at beginning of period	97,126	145,181
Cash and cash equivalents at end of period	155,783	193,757
Supplemental disclosures of cash flow information:
Interest paid	8,127	6,075
Income taxes paid	25,696	40,787
Detail of acquisitions:
Fair value of assets acquired	11,889	22,202
Cash paid for acquisitions	(11,445)	(19,350)
Holdbacks	(500)	(7)
Liabilities assumed	$ (56)	$ 2,845