Geographic Information (Schedule Of Net Revenue And Long-Lived Assets By Geographic Area) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended										12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010		Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Net revenues	$ 172,420		$ 167,627	$ 156,985	$ 145,372	$ 144,900		$ 140,545	$ 130,649	$ 116,039	$ 642,404	[1]	$ 532,133	[1]	$ 419,006	[1]
Long-lived assets	106,908	[2]				103,013	[2]				106,908	[2]	103,013	[2]	90,546	[2]
North America [Member]
Net revenues											594,352	[1],[3]	492,310	[1],[3]	385,433	[1],[3]
Long-lived assets	1,558	[2],[3]				1,818	[2],[3]				1,558	[2],[3]	1,818	[2],[3]	1,826	[2],[3]
India [Member]
Net revenues											2,603	[1]	1,777	[1]	3,164	[1]
Long-lived assets	105,262	[2]				101,145	[2]				105,262	[2]	101,145	[2]	88,668	[2]
Europe [Member]
Net revenues											43,346	[1],[4]	35,689	[1],[4]	29,172	[1],[4]
Long-lived assets	88	[2],[4]				50	[2],[4]				88	[2],[4]	50	[2],[4]	52	[2],[4]
Rest Of The World [Member]
Net revenues											$ 2,103	[1]	$ 2,357	[1]	$ 1,237	[1]

[1] Net revenues are attributed to regions based upon customer location.

[2] Long-lived assets include property and equipment, net of accumulated depreciation and amortization and goodwill.

[3] Primarily relates to operations in the United States.

[4] Primarily relates to operations in the United Kingdom.