Business and Geographic Segments (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Business and Geographic Segments
Sales to international customers									$ 26,000	$ 28,000	$ 40,000
Geographic Segments
Service and Sales Revenue:	239,079	222,739	220,248	196,656	212,066	221,061	233,033	216,339	878,722	882,499	927,749
Long-lived assets (excluding identifiable intangibles):	426,488				450,581				426,488	450,581
United States
Geographic Segments
Service and Sales Revenue:									425,665	470,639	477,175
Long-lived assets (excluding identifiable intangibles):	205,868				195,718				205,868	195,718
International
Geographic Segments
Service and Sales Revenue:									453,057	411,860	450,574
Long-lived assets (excluding identifiable intangibles):	220,620				254,863				220,620	254,863
North America, other than United States
Geographic Segments
Service and Sales Revenue:									58,103	66,526	53,139
Long-lived assets (excluding identifiable intangibles):	40,981				47,960				40,981	47,960
United Kingdom
Geographic Segments
Service and Sales Revenue:									136,286	87,029	82,628
Long-lived assets (excluding identifiable intangibles):	92,849				115,223				92,849	115,223
Europe
Geographic Segments
Service and Sales Revenue:									183,063	178,578	226,006
Long-lived assets (excluding identifiable intangibles):	28,902				26,424				28,902	26,424
Other
Geographic Segments
Service and Sales Revenue:									75,605	79,727	88,801
Long-lived assets (excluding identifiable intangibles):	$ 57,888				$ 65,256				$ 57,888	$ 65,256