Geographic Information (Summary Of Distribution Of Assets By Geographic Region) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Tangible assets	$ 413,096	$ 405,644
Assets as a percentage of total assets	100.00%	100.00%
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Tangible assets	337,327	338,779
Assets as a percentage of total assets	81.70%	83.50%
UNITED KINGDOM
Revenues from External Customers and Long-Lived Assets [Line Items]
Tangible assets	24,633	25,207
Assets as a percentage of total assets	6.00%	6.20%
INDIA
Revenues from External Customers and Long-Lived Assets [Line Items]
Tangible assets	8,368	8,449
Assets as a percentage of total assets	2.00%	2.10%
NEW ZEALAND
Revenues from External Customers and Long-Lived Assets [Line Items]
Tangible assets	8,213	7,508
Assets as a percentage of total assets	2.00%	1.90%
CHINA
Revenues from External Customers and Long-Lived Assets [Line Items]
Tangible assets	7,749	6,676
Assets as a percentage of total assets	1.90%	1.60%
GERMANY
Revenues from External Customers and Long-Lived Assets [Line Items]
Tangible assets	11,351	5,663
Assets as a percentage of total assets	2.70%	1.40%
Other Country [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Tangible assets	$ 15,455	$ 13,362
Assets as a percentage of total assets	3.70%	3.30%