Segment Reporting (Schedule Of Revenue By Principal Geographic Area) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 354,073	$ 338,297	$ 352,583	$ 332,106	$ 319,538	$ 315,475	$ 335,649	$ 322,676	$ 1,377,058	$ 1,293,338	$ 1,218,689
Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									899,185	848,725	785,839
Americas [Member] | United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									802,345	759,419	700,090
Americas [Member] | Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									69,947	66,405	65,318
Americas [Member] | Other Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									26,893	22,901	20,431
Europe, The Middle East And Africa [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									326,685	300,638	311,637
Europe, The Middle East And Africa [Member] | Germany [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									78,109	72,983	78,806
Europe, The Middle East And Africa [Member] | United Kingdom [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									65,027	64,412	61,016
Europe, The Middle East And Africa [Member] | France [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									49,093	45,927	48,164
Europe, The Middle East And Africa [Member] | Italy [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									26,443	24,625	26,320
Europe, The Middle East And Africa [Member] | Spain [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									20,194	19,776	22,622
Europe, The Middle East And Africa [Member] | Other Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									87,819	72,915	74,709
Asia Pacific Region [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									151,188	143,975	121,213
Asia Pacific Region [Member] | Australia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									53,063	50,658	44,023
Asia Pacific Region [Member] | Japan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									44,869	49,204	43,445
Asia Pacific Region [Member] | China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									29,044	24,628	17,288
Asia Pacific Region [Member] | Other Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									$ 24,212	$ 19,485	$ 16,457