Fair Value Measurements (Details) - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
Financial Assets:
Held-to-maturity Securities, Fair Value		$ 2,949
Fair Value Measurements, Recurring [Member]
Financial Assets:
Total		3,019
Financial Liabilities:
Common stock warrant liability	[1]	4	$ 69
Total		4	69
Fair Value Measurements, Recurring [Member] | Corporate Fixed Income Debt Securities [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value		2,949
Fair Value Inputs, Level 1 [Member] | Fair Value Measurements, Recurring [Member]
Financial Assets:
Total		70
Financial Liabilities:
Common stock warrant liability	[1]
Total
Fair Value Inputs, Level 1 [Member] | Fair Value Measurements, Recurring [Member] | Corporate Fixed Income Debt Securities [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value
Fair Value Inputs, Level 2 [Member] | Fair Value Measurements, Recurring [Member]
Financial Assets:
Total		2,949
Financial Liabilities:
Common stock warrant liability	[1]
Total
Fair Value Inputs, Level 2 [Member] | Fair Value Measurements, Recurring [Member] | Corporate Fixed Income Debt Securities [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value		2,949
Fair Value Inputs, Level 3 [Member] | Fair Value Measurements, Recurring [Member]
Financial Assets:
Total
Financial Liabilities:
Common stock warrant liability	[1]	4	69
Total		4	$ 69
Fair Value Inputs, Level 3 [Member] | Fair Value Measurements, Recurring [Member] | Corporate Fixed Income Debt Securities [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value
Money Market Funds [Member] | Fair Value Measurements, Recurring [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value		70
Money Market Funds [Member] | Fair Value Inputs, Level 1 [Member] | Fair Value Measurements, Recurring [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value		70
Money Market Funds [Member] | Fair Value Inputs, Level 2 [Member] | Fair Value Measurements, Recurring [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value
Money Market Funds [Member] | Fair Value Inputs, Level 3 [Member] | Fair Value Measurements, Recurring [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value

[1] The change in the fair value of the common stock warrant and convertible notes payable for the three and nine months ended September 30, 2017 was recorded as a decrease to other income (expense) and interest expense of $30 and $69, respectively, in the statements of operations and comprehensive loss.