Cash, Cash Equivalents, and Available-For-Sale Investments (Details 1) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Total cash, cash equivalents, and available-for-sale investments	$ 481,847	$ 315,932
Corporate notes and bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Total cash, cash equivalents, and available-for-sale investments	360,536	190,527
U.S. corporate commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Total cash, cash equivalents, and available-for-sale investments	101,434	82,361
Obligations of U.S. government agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Total cash, cash equivalents, and available-for-sale investments	8,251	25,289
Cash and money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Total cash, cash equivalents, and available-for-sale investments	$ 11,626	$ 17,755