Segment Reporting (Schedule Of Net Long-Lived Assets By Principal Geographic Areas) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	$ 245,177	$ 216,777
Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	211,212	190,144
Americas [Member] | United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	208,725	187,621
Americas [Member] | Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	2,487	2,523
Europe, the Middle East and Africa [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	29,373	22,787
Europe, the Middle East and Africa [Member] | United Kingdom [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	12,440	11,000
Europe, the Middle East and Africa [Member] | Germany [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	6,144	2,360
Europe, the Middle East and Africa [Member] | Switzerland [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	3,411	2,547
Europe, the Middle East and Africa [Member] | France [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	3,079	2,270
Europe, the Middle East and Africa [Member] | Netherlands [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	3,034	3,400
Europe, the Middle East and Africa [Member] | Other Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	1,265	1,210
Asia Pacific Region [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	4,592	3,846
Asia Pacific Region [Member] | Japan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	1,016	1,142
Asia Pacific Region [Member] | Australia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	2,484	1,495
Asia Pacific Region [Member] | Other Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net Assets	$ 1,092	$ 1,209