Fair Value Measurements (Details 1) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value, Level 1
Fair Value
Cash and Cash Equivalents	$ 38,772	$ 200,526
Short-term Investments	319,078	312,888
Total Cash and Cash Equivalents and Investments	357,850	513,414
Accrued Liabilities	0	0
Other Long-term Liabilities		0
Total Liabilities	0	0
Fair Value, Level 2
Fair Value
Cash and Cash Equivalents	0	2,463
Short-term Investments	37,706	5,475
Total Cash and Cash Equivalents and Investments	37,706	7,938
Accrued Liabilities	0	0
Other Long-term Liabilities		0
Total Liabilities	0	0
Fair Value, Level 3
Fair Value
Cash and Cash Equivalents	0	0
Short-term Investments	0	0
Total Cash and Cash Equivalents and Investments	0	0
Accrued Liabilities	18,912	12,453
Other Long-term Liabilities		10,362
Total Liabilities	18,912	22,815
Fair Value, Total
Fair Value
Cash and Cash Equivalents	38,772	202,989
Short-term Investments	356,784	318,363
Total Cash and Cash Equivalents and Investments	395,556	521,352
Accrued Liabilities	18,912	12,453
Other Long-term Liabilities		10,362
Total Liabilities	$ 18,912	$ 22,815