Fair Value Measurements (Details 1) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Fair Value, Level 1
Fair Value
Cash and Cash Equivalents	$ 9,744	$ 137,266
Short-term Investments	272,186	201,521
Total Cash and Cash Equivalents and Investments	281,930	338,787
Other Long-term Liabilities	0	0
Total Liabilities	0	0
Fair Value, Level 2
Fair Value
Cash and Cash Equivalents	0	0
Short-term Investments	553	552
Total Cash and Cash Equivalents and Investments	553	552
Other Long-term Liabilities	0	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
Other Long-term Liabilities	18,629	17,638
Total Liabilities	18,629	17,638
Fair Value, Total
Fair Value
Cash and Cash Equivalents	9,744	137,266
Short-term Investments	272,739	202,073
Total Cash and Cash Equivalents and Investments	282,483	339,339
Other Long-term Liabilities	18,629	17,638
Total Liabilities	$ 18,629	$ 17,638