Segment Reporting (Schedule Of Revenue By Principal Geographic Area) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 351,959	$ 383,523	$ 390,122	$ 360,203	$ 354,073	$ 338,297	$ 352,583	$ 332,106	$ 1,485,807	$ 1,377,058	$ 1,293,338
Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									952,757	899,185	848,725
Americas [Member] | United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									848,928	802,345	759,419
Americas [Member] | Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									69,743	69,947	66,405
Americas [Member] | Latin America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									34,086	26,893	22,901
Europe, The Middle East And Africa [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									366,390	326,685	300,638
Europe, The Middle East And Africa [Member] | Germany [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									85,189	78,109	72,983
Europe, The Middle East And Africa [Member] | United Kingdom [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									74,131	65,027	64,412
Europe, The Middle East And Africa [Member] | France [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									53,322	49,093	45,927
Europe, The Middle East And Africa [Member] | Italy [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									28,794	26,443	24,625
Europe, The Middle East And Africa [Member] | Spain [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									21,566	20,194	19,776
Europe, The Middle East And Africa [Member] | Switzerland [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									14,544	12,246	12,967
Europe, The Middle East And Africa [Member] | Other Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									88,844	75,573	59,948
Asia Pacific Region [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									166,660	151,188	143,975
Asia Pacific Region [Member] | Australia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									58,448	53,063	50,658
Asia Pacific Region [Member] | Japan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									44,132	44,869	49,204
Asia Pacific Region [Member] | China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									34,674	29,044	24,628
Asia Pacific Region [Member] | Other Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									$ 29,406	$ 24,212	$ 19,485