Guarantor Subsidiaries (Schedule Of Guarantor Subsidiaries - Balance Sheet) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Guarantor Subsidairies [Line Items]
Cash and cash equivalents	$ 69,296	$ 38,081	$ 21,342	$ 49,917
Accounts receivable, less allowances	101,152	77,924
Inventories - net	7,639	8,668
Current deferred income taxes	14,118	12,540
Prepaid income taxes	3,044	2,131
Prepaid expenses	9,855	11,409
Total current assets	205,104	150,753
Investments of deferred compensation plans	35,053	31,629
Properties and equipment, at cost, less accumulated depreciation	90,135	82,951
Identifiable intangible assets less accumulated amortization	57,507	58,262
Goodwill	465,861	460,633
Other assets	11,127	11,677
Total Assets	864,787	795,905
Accounts payable	44,056	48,225
Income taxes	1,496	90
Accrued insurance	39,518	37,147
Accrued compensation	44,117	41,087
Other current liabilities	18,494	18,851
Total current liabilities	147,681	145,400
Deferred income taxes	24,264	29,463
Long-term debt	172,812	166,784
Deferred compensation liabilities	34,626	30,693
Other liabilities	10,779	9,881
Stockholders' equity	474,625	413,684
Total Liabilities and Stockholders' Equity	864,787	795,905
Parent [Member]
Guarantor Subsidairies [Line Items]
Cash and cash equivalents	58,449	32,470	15,950	45,324
Accounts receivable, less allowances	955	606
Current deferred income taxes	(1,628)	(650)
Prepaid income taxes	5,251	(114)
Prepaid expenses	730	503
Total current assets	63,757	32,815
Properties and equipment, at cost, less accumulated depreciation	11,132	11,641
Other assets	6,396	7,616
Investments in subsidiaries	852,204	793,277
Total Assets	933,489	845,349
Accounts payable	(5,239)	(683)
Intercompany payables	294,307	269,042
Income taxes	(818)
Accrued insurance	1,288	489
Accrued compensation	3,075	3,828
Other current liabilities	3,124	1,719
Total current liabilities	295,737	274,395
Deferred income taxes	(12,830)	(12,330)
Long-term debt	172,812	166,784
Other liabilities	3,145	2,816
Stockholders' equity	474,625	413,684
Total Liabilities and Stockholders' Equity	933,489	845,349
Guarantor Subsidiaries [Member]
Guarantor Subsidairies [Line Items]
Cash and cash equivalents	3,010	(1,422)	(1,449)	(1,571)
Accounts receivable, less allowances	99,639	76,816
Intercompany receivables	298,490	273,413
Inventories - net	6,946	8,032
Current deferred income taxes	15,512	13,059
Prepaid income taxes	(1,799)	1,689
Prepaid expenses	8,935	10,757
Total current assets	430,733	382,344
Properties and equipment, at cost, less accumulated depreciation	76,273	68,755
Identifiable intangible assets less accumulated amortization	57,507	58,262
Goodwill	461,277	456,183
Other assets	1,765	1,552
Investments in subsidiaries	24,205	21,148
Total Assets	1,051,760	988,244
Accounts payable	48,934	48,490
Income taxes	601
Accrued insurance	38,230	36,658
Accrued compensation	40,595	36,655
Other current liabilities	15,017	15,728
Total current liabilities	143,377	137,531
Deferred income taxes	47,968	51,601
Deferred compensation liabilities	33
Other liabilities	6,875	4,630
Stockholders' equity	853,507	794,482
Total Liabilities and Stockholders' Equity	1,051,760	988,244
Non-Guarantor Subsidiaries [Member]
Guarantor Subsidairies [Line Items]
Cash and cash equivalents	7,837	7,033	6,841	6,164
Accounts receivable, less allowances	558	502
Inventories - net	693	636
Current deferred income taxes	234	131
Prepaid income taxes	(408)	556
Prepaid expenses	190	149
Total current assets	9,104	9,007
Investments of deferred compensation plans	35,053	31,629
Properties and equipment, at cost, less accumulated depreciation	2,730	2,555
Goodwill	4,584	4,450
Other assets	2,966	2,509
Total Assets	54,437	50,150
Accounts payable	361	418
Intercompany payables	4,183	4,371
Income taxes	1,713	90
Accrued compensation	447	604
Other current liabilities	353	1,404
Total current liabilities	7,057	6,887
Deferred income taxes	(10,874)	(9,808)
Deferred compensation liabilities	34,593	30,693
Other liabilities	759	2,435
Stockholders' equity	22,902	19,943
Total Liabilities and Stockholders' Equity	54,437	50,150
Consolidating Adjustments [Member]
Guarantor Subsidairies [Line Items]
Intercompany receivables	(298,490)	(273,413)
Total current assets	(298,490)	(273,413)
Investments in subsidiaries	(876,409)	(814,425)
Total Assets	(1,174,899)	(1,087,838)
Intercompany payables	(298,490)	(273,413)
Total current liabilities	(298,490)	(273,413)
Stockholders' equity	(876,409)	(814,425)
Total Liabilities and Stockholders' Equity	$ (1,174,899)	$ (1,087,838)