Cash, Cash Equivalents, and Available-For-Sale Investments (Details 3) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Fair value assets measured on recurring basis
Cash	$ 1,032	$ 1,727
Total cash, cash equivalents, and available-for-sale investments	481,847	315,932
Corporate notes and bonds [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	360,536	190,527
Corporate notes and bonds [Member] | Level 1 [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	0	0
Corporate notes and bonds [Member] | Level 2 [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	360,536	190,527
Corporate notes and bonds [Member] | Level 3 [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	0	0
U.S. corporate commercial paper [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	101,434	82,361
U.S. corporate commercial paper [Member] | Level 1 [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	0	0
U.S. corporate commercial paper [Member] | Level 2 [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	101,434	82,361
U.S. corporate commercial paper [Member] | Level 3 [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	0	0
Obligations of U.S. government agencies [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	8,251	25,289
Obligations of U.S. government agencies [Member] | Level 1 [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	0	0
Obligations of U.S. government agencies [Member] | Level 2 [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	8,251	25,289
Obligations of U.S. government agencies [Member] | Level 3 [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	0	0
Money market funds [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	10,594	16,028
Money market funds [Member] | Level 1 [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	10,594	16,028
Money market funds [Member] | Level 2 [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	0	0
Money market funds [Member] | Level 3 [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	0	0
Cash equivalents and available-for-sale investments [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	480,815	314,205
Cash equivalents and available-for-sale investments [Member] | Level 1 [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	10,594	16,028
Cash equivalents and available-for-sale investments [Member] | Level 2 [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	470,221	298,177
Cash equivalents and available-for-sale investments [Member] | Level 3 [Member]
Fair value assets measured on recurring basis
Total cash, cash equivalents, and available-for-sale investments	$ 0	$ 0