Guarantor Subsidiaries (Schedule Of Guarantor Subsidiaries - Income Statement) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Condensed Income Statements, Captions [Line Items]
Service revenues and sales	$ 340,886	$ 354,353	$ 1,064,725	$ 1,061,466
Cost of services provided and goods sold	243,184	256,610	762,850	771,423
Selling, general and administrative expenses	48,870	52,955	157,537	155,892
Depreciation	6,971	6,557	20,665	19,178
Amortization	1,190	1,135	3,498	3,375
Other operating expenses	11,461	1,126	26,221	1,126
Total costs and expenses	311,676	318,383	970,771	950,994
Income/ (loss) from operations	29,210	35,970	93,954	110,472
Interest expense	(3,500)	(3,743)	(11,291)	(11,032)
Other (expense)/income - net	(90)	1,840	3,312	2,965
Income/(loss) before income taxes	25,620	34,067	85,975	102,405
Income tax (provision)/ benefit	(8,188)	(13,222)	(31,657)	(39,841)
Net income	17,432	20,845	54,318	62,564
Consolidating Adjustments [Member]
Condensed Income Statements, Captions [Line Items]
Equity in net income of subsidiaries	(23,414)	(25,634)	(70,390)	(76,551)
Net income	(23,414)	(25,634)	(70,390)	(76,551)
Parent [Member]
Condensed Income Statements, Captions [Line Items]
Selling, general and administrative expenses	5,562	5,991	17,290	17,124
Depreciation	240	237	718	704
Amortization	501	486	1,480	1,437
Total costs and expenses	6,303	6,714	19,488	19,265
Income/ (loss) from operations	(6,303)	(6,714)	(19,488)	(19,265)
Interest expense	(3,579)	(3,517)	(11,089)	(10,437)
Other (expense)/income - net	3,944	4,450	12,526	13,196
Income/(loss) before income taxes	(5,938)	(5,781)	(18,051)	(16,506)
Income tax (provision)/ benefit	2,042	1,877	6,036	5,376
Equity in net income of subsidiaries	21,328	24,749	66,333	73,694
Net income	17,432	20,845	54,318	62,564
Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Service revenues and sales	333,750	347,384	1,042,449	1,040,015
Cost of services provided and goods sold	239,122	252,688	750,230	759,549
Selling, general and administrative expenses	42,113	43,992	133,419	131,695
Depreciation	6,497	6,099	19,241	17,816
Amortization	689	649	2,018	1,938
Other operating expenses	11,461	1,126	26,221	1,126
Total costs and expenses	299,882	304,554	931,129	912,124
Income/ (loss) from operations	33,868	42,830	111,320	127,891
Interest expense	(131)	(211)	(384)	(551)
Other (expense)/income - net	(3,840)	(4,184)	(11,549)	(12,982)
Income/(loss) before income taxes	29,897	38,435	99,387	114,358
Income tax (provision)/ benefit	(11,393)	(14,560)	(37,755)	(43,442)
Equity in net income of subsidiaries	2,086	885	4,057	2,857
Net income	20,590	24,760	65,689	73,773
Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Service revenues and sales	7,136	6,969	22,276	21,451
Cost of services provided and goods sold	4,062	3,922	12,620	11,874
Selling, general and administrative expenses	1,195	2,972	6,828	7,073
Depreciation	234	221	706	658
Total costs and expenses	5,491	7,115	20,154	19,605
Income/ (loss) from operations	1,645	(146)	2,122	1,846
Interest expense	210	(15)	182	(44)
Other (expense)/income - net	(194)	1,574	2,335	2,751
Income/(loss) before income taxes	1,661	1,413	4,639	4,553
Income tax (provision)/ benefit	1,163	(539)	62	(1,775)
Net income	$ 2,824	$ 874	$ 4,701	$ 2,778