Fair Value Measurements - Summary of Financial Instruments Measured on a Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial assets	$ 7,450	$ 35,656
Fair value of financial liabilities	2,154	6,601
Warrant liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial liabilities	2,154	6,601
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial assets	7,450	35,656
Fair value of financial liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Warrant liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial liabilities	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial assets	0	0
Fair value of financial liabilities	0	0
Significant Other Observable Inputs (Level 2) | Warrant liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial liabilities	0	0
Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial assets	0	0
Fair value of financial liabilities	2,154	6,601
Significant Unobservable Inputs (Level 3) | Warrant liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial liabilities	2,154	6,601
Cash on deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial assets	894	9,767
Cash on deposit | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial assets	894	9,767
Cash on deposit | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial assets	0	0
Cash on deposit | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial assets	0	0
Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial assets	6,556	25,889
Money market funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial assets	6,556	25,889
Money market funds | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial assets	0	0
Money market funds | Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of financial assets	$ 0	$ 0