Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Cash flows from operating activities:
Net income	$ 132,756	$ 135,503
Adjustments to reconcile net income to net cash provided by operating activities:
Bad debt expense	27,107	23,406
Depreciation and amortization expense	91,976	87,847
Net loss (gain) on disposal of property and equipment	60	(26)
Amortization of debt issuance costs	1,368	1,327
Amortization of discount on bonds payable	14,745	13,750
Stock-based compensation expense	15,863	19,793
Deferred income taxes	38,212	34,589
Excess tax benefit from stock-based compensation	(240)	(394)
Change in assets and liabilities net of effects of acquired businesses:
Accounts receivable	(69,188)	(56,530)
Inventories	893	5,187
Prepaid and other assets	(3,142)	1,514
Accounts payable	(12,299)	488
Accrued expenses and other current liabilities	(27,334)	10,271
Income taxes payable	8,821	(11,437)
Long-term obligations	(2,386)	(6,125)
Net cash provided by operating activities	217,212	259,163
Cash flows from investing activities:
Proceeds from sale of property and equipment	238	49
Capital expenditures	(95,934)	(80,380)
Purchases of investments	(40,000)	(20,000)
Sales and maturities of investments	60,000	58,650
Business acquisitions, net of cash acquired	(95,634)	(11,375)
Cash restricted for future payments	345	(5,345)
Net cash used in investing activities	(170,985)	(58,401)
Cash flows from financing activities:
Net proceeds from revolving credit line	80,000	0
Payments of principal on debt	(9,102)	(1,034)
Payments of debt issuance costs	(1,783)	0
Payments of cash dividends	(57,141)	(19,617)
Proceeds from exercise of stock options and issuance of common shares	14,147	26,126
Excess tax benefit from stock-based compensation	240	394
Payments to acquire treasury stock	(199,987)	(49,961)
Net cash used in financing activities	(173,626)	(44,092)
Net (decrease) increase in cash and cash equivalents	(127,399)	156,670
Cash and cash equivalents, beginning of period	164,203	20,428
Cash and cash equivalents, end of period	36,804	177,098
Supplemental disclosure of cash flow information:
Cash paid for interest	7,665	7,563
Cash paid for income taxes	$ 38,343	$ 65,504