Fair Value Measurements (Short-term Investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	$ 104,793	$ 167,382
Short-term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	51,814	$ 58,453
Estimated Fair Value | Short-term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	51,814
Estimated Fair Value | Within one year | Short-term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	51,389
Estimated Fair Value | Between one year and five years | Short-term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	$ 425