Segment Reporting (Schedule Of Revenue By Principal Geographic Area) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 319,538	$ 315,475	$ 335,649	$ 322,676	$ 307,201	$ 300,954	$ 317,862	$ 292,672	$ 1,293,338	$ 1,218,689	$ 1,103,392
Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									848,725	785,839	728,175
Americas [Member] | United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									759,419	700,090	652,026
Americas [Member] | Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									66,405	65,318	59,806
Americas [Member] | Latin America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									22,901	20,431	16,343
Europe, the Middle East and Africa [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									300,638	311,637	273,892
Europe, the Middle East and Africa [Member] | Germany [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									72,983	78,806	68,318
Europe, the Middle East and Africa [Member] | United Kingdom [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									64,412	61,016	56,493
Europe, the Middle East and Africa [Member] | France [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									45,927	48,164	42,895
Europe, the Middle East and Africa [Member] | Italy [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									24,625	26,320	22,173
Europe, the Middle East and Africa [Member] | Spain [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									19,776	22,622	20,244
Europe, the Middle East and Africa [Member] | Other Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									72,915	74,709	63,769
Asia Pacific Region [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									143,975	121,213	101,325
Asia Pacific Region [Member] | Australia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									50,658	44,023	36,296
Asia Pacific Region [Member] | Japan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									49,204	43,445	36,260
Asia Pacific Region [Member] | China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									24,628	17,288	15,108
Asia Pacific Region [Member] | Other Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									$ 19,485	$ 16,457	$ 13,661