Stockholders' Equity (chedule of Stock Based Compensation Expense (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of stock-based compensation on income	$ 24,801	$ 25,621	$ 47,732	$ 46,545
Less: Income tax benefit	(9,345)	(9,375)	(16,309)	(17,872)
Total stock-based compensation, net of taxes	15,456	16,246	31,423	28,673
Cost of Revenue [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of stock-based compensation on income	2,718	3,063	5,345	5,769
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of stock-based compensation on income	3,867	4,901	8,236	8,831
Sales and Marketing Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of stock-based compensation on income	9,799	8,814	19,230	16,925
General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of stock-based compensation on income	8,417	8,843	14,921	15,020
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of stock-based compensation on income	3,104	4,366	6,293	7,466
Deferred Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of stock-based compensation on income	1,705	1,885	1,705	1,885
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of stock-based compensation on income	21,608	19,734	42,526	38,462
Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of stock-based compensation on income	1,629	1,471	3,391	2,865
Capitalized Internal Use Software [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Effect of stock-based compensation on income	$ (3,245)	$ (1,835)	$ (6,183)	$ (4,133)