Stock-Based Compensation - Reserved Shares (Details) shares in Thousands	Dec. 31, 2016 shares
Stock-Based Compensation
Reserved shares of common stock for future issuance	2,437
2000 Stock Incentive Plan
Stock-Based Compensation
Reserved shares of common stock for future issuance	55
2009 Stock Incentive Plan
Stock-Based Compensation
Reserved shares of common stock for future issuance	1,935
2009 Employee Stock Purchase Plan
Stock-Based Compensation
Reserved shares of common stock for future issuance	447