Stock-Based Compensation (Classification Of Stock-Based Compensation Expense) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010
Total stock-based compensation	$ 5,492		$ 4,515		$ 12,906		$ 9,170
Tax benefit associated with stock-based compensation expense	2,125	[1]	1,747	[1]	4,995	[1]	3,549	[1]
Reduction of net income	3,367		2,768		7,911		5,621
Percentage of recognized tax benefit related to share-based compensation expense	38.70%		38.70%		38.70%		38.70%
Cost of Services [Member]
Total stock-based compensation	238		199		554		383
Sales and Marketing [Member]
Total stock-based compensation	1,682		1,246		3,791		2,359
Research and Development [Member]
Total stock-based compensation	1,614		1,592		3,767		3,010
General and Administrative [Member]
Total stock-based compensation	$ 1,958		$ 1,478		$ 4,794		$ 3,418

[1] The recognized tax benefit related to share-based compensation expense is estimated to be 38.7% for the three months and six months ended June 30, 2011 and 2010. This approximates the blended Federal and State statutory tax rate after the benefit for state taxes.