Guarantor Subsidiaries (Schedule Of Guarantor Subsidiaries - Income Statement) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Service revenues and sales	$ 352,943	$ 330,918
Cost of services provided and goods sold	257,445	237,458
Selling, general and administrative expenses	53,167	55,654
Depreciation	6,241	6,288
Amortization	1,113	970
Total costs and expenses	317,966	300,370
Income/ (loss) from operations	34,977	30,548
Interest expense	(3,617)	(3,244)
Other (expense)/income - net	2,095	2,102
Income before income taxes	33,455	29,406
Income tax (provision)/ benefit	(13,010)	(11,305)
Net income	20,445	18,101
Parent [Member]
Selling, general and administrative expenses	5,196	6,684
Depreciation	234	239
Amortization	469	355
Total costs and expenses	5,899	7,278
Income/ (loss) from operations	(5,899)	(7,278)
Interest expense	(3,433)	(3,132)
Other (expense)/income - net	4,406	3,770
Income before income taxes	(4,926)	(6,640)
Income tax (provision)/ benefit	1,581	2,403
Equity in net income of subsidiaries	23,790	22,338
Net income	20,445	18,101
Guarantor Subsidiaries [Member]
Service revenues and sales	345,614	324,157
Cost of services provided and goods sold	253,427	233,876
Selling, general and administrative expenses	44,347	45,581
Depreciation	5,790	5,862
Amortization	644	615
Total costs and expenses	304,208	285,934
Income/ (loss) from operations	41,406	38,223
Interest expense	(169)	(112)
Other (expense)/income - net	(4,441)	(3,729)
Income before income taxes	36,796	34,382
Income tax (provision)/ benefit	(13,964)	(13,052)
Equity in net income of subsidiaries	982	1,033
Net income	23,814	22,363
Non-Guarantor Subsidiaries [Member]
Service revenues and sales	7,329	6,761
Cost of services provided and goods sold	4,018	3,582
Selling, general and administrative expenses	3,624	3,389
Depreciation	217	187
Total costs and expenses	7,859	7,158
Income/ (loss) from operations	(530)	(397)
Interest expense	(15)
Other (expense)/income - net	2,130	2,061
Income before income taxes	1,585	1,664
Income tax (provision)/ benefit	(627)	(656)
Net income	958	1,008
Consolidating Adjustments [Member]
Equity in net income of subsidiaries	(24,772)	(23,371)
Net income	$ (24,772)	$ (23,371)