Fair Value Measurements (Short-term Investments) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	$ 117,522	$ 167,382
Short-term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	18,337	$ 58,453
Estimate of Fair Value Measurement | Short-term Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	18,337
Estimate of Fair Value Measurement | Short-term Investments | Within one year
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	16,915
Estimate of Fair Value Measurement | Short-term Investments | Between one year and five years
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets fair value	$ 1,422