Stockholders' Equity (Schedule of Stock Based Compensation Expense) (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation before income taxes	$ 11,612	$ 20,276	$ 27,324	$ 39,384
Less: Income tax benefit	(4,311)	(7,271)	(9,373)	(14,999)
Total stock-based compensation, net of taxes	7,301	13,005	17,951	24,385
Cost of Revenue [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of stock-based compensation on income	590	707	1,145	1,408
General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of stock-based compensation on income	3,583	7,251	9,132	12,641
Sales and Marketing Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of stock-based compensation on income	5,315	8,776	12,161	17,800
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of stock-based compensation on income	2,124	3,542	4,886	7,535
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation before income taxes	3,420	3,628	7,206	7,397
Deferred Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation before income taxes	1,885	1,885	1,885	1,885
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation before income taxes	6,528	15,909	18,648	31,593
1999 ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation before income taxes	1,420	1,056	3,050	2,188
Capitalized Internal Use Software [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation before income taxes	$ (1,641)	$ (2,202)	$ (3,465)	$ (3,679)