Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Assets:
Total assets	$ 69,638	$ 15,490
Liabilities:
Total liabilities	1,632	8,795
Derivative Liability
Liabilities:
Total liabilities	1,632	8,795
Money Market Funds
Assets:
Total assets	22,169	6,522
Short-term Investments - Certificates of Deposit
Assets:
Total assets		8,628
Investment
Assets:
Total assets	330	340
Short-term Investments - Commercial Paper
Assets:
Total assets	19,945
Short-term Investments - Corporate Notes
Assets:
Total assets	10,017
Short-term investments - U.S. Government Bonds
Assets:
Total assets	17,177
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Total assets	22,499	15,490
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money Market Funds
Assets:
Total assets	22,169	6,522
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments - Certificates of Deposit
Assets:
Total assets		8,628
Quoted Prices in Active Markets for Identical Assets (Level 1) | Investment
Assets:
Total assets	330	340
Significant Other Observable Inputs (Level 2)
Assets:
Total assets	47,139
Significant Other Observable Inputs (Level 2) | Short-term Investments - Commercial Paper
Assets:
Total assets	19,945
Significant Other Observable Inputs (Level 2) | Short-term Investments - Corporate Notes
Assets:
Total assets	10,017
Significant Other Observable Inputs (Level 2) | Short-term investments - U.S. Government Bonds
Assets:
Total assets	17,177
Significant Unobservable Inputs (Level 3)
Liabilities:
Total liabilities	1,632	8,795
Significant Unobservable Inputs (Level 3) | Derivative Liability
Liabilities:
Total liabilities	$ 1,632	$ 8,795