Geographic Information (Schedule Of Revenue By Geographic Region) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Total, Amount	$ 86,284	$ 69,015	$ 164,086	$ 128,993
Percent of Revenues	100.00%	100.00%	100.00%	100.00%
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Total, Amount	60,915	50,412	118,730	94,962
Percent of Revenues	70.60%	73.00%	72.40%	73.60%
UNITED KINGDOM
Revenues from External Customers and Long-Lived Assets [Line Items]
Total, Amount	8,965	6,336	15,952	11,497
Percent of Revenues	10.40%	9.20%	9.70%	9.00%
Other European Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total, Amount	4,960	4,278	9,387	7,558
Percent of Revenues	5.70%	6.20%	5.70%	5.80%
CANADA
Revenues from External Customers and Long-Lived Assets [Line Items]
Total, Amount	2,744	1,637	5,623	3,232
Percent of Revenues	3.20%	2.40%	3.40%	2.50%
CHINA
Revenues from External Customers and Long-Lived Assets [Line Items]
Total, Amount	2,541	2,432	4,093	3,852
Percent of Revenues	2.90%	3.50%	2.50%	3.00%
GERMANY
Revenues from External Customers and Long-Lived Assets [Line Items]
Total, Amount	1,684	1,501	2,781	2,835
Percent of Revenues	2.00%	2.20%	1.70%	2.20%
Other Country [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total, Amount	$ 4,475	$ 2,419	$ 7,520	$ 5,057
Percent of Revenues	5.20%	3.50%	4.60%	3.90%