Stock-Based Compensation (Classification Of Stock-Based Compensation Expense) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Total stock-based compensation	$ 5,514		$ 6,356		$ 18,420		$ 15,526
Tax benefit associated with stock-based compensation expense	2,134	[1]	2,460	[1]	7,129	[1]	6,009	[1]
Reduction of net income	3,380		3,896		11,291		9,517
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	244		329		798		711
Sales And Marketing [Member]
Total stock-based compensation	1,653		1,991		5,444		4,352
Research And Development [Member]
Total stock-based compensation	1,679		2,336		5,445		5,346
General And Administrative [Member]
Total stock-based compensation	$ 1,938		$ 1,700		$ 6,733		$ 5,117

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