Fair Value Measurements (Details) - Fair Value Measurements, Recurring [Member] - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Financial Assets:
Held-to-maturity Securities, Fair Value
Total
Financial Liabilities:
Common stock warrant liability	[1]	$ 5
Total		5
Corporate Fixed Income Debt Securities [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value
Total
Money Market Funds [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value
Total
Fair Value Inputs, Level 1 [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value
Total
Financial Liabilities:
Common stock warrant liability	[1]
Total
Fair Value Inputs, Level 1 [Member] | Corporate Fixed Income Debt Securities [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value
Total
Fair Value Inputs, Level 1 [Member] | Money Market Funds [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value
Total			3
Fair Value Inputs, Level 2 [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value
Total
Financial Liabilities:
Common stock warrant liability	[1]
Total
Fair Value Inputs, Level 2 [Member] | Corporate Fixed Income Debt Securities [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value
Total
Fair Value Inputs, Level 2 [Member] | Money Market Funds [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value
Total
Fair Value Inputs, Level 3 [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value
Total
Financial Liabilities:
Common stock warrant liability	[1]	5
Total		$ 5
Fair Value Inputs, Level 3 [Member] | Corporate Fixed Income Debt Securities [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value
Total
Fair Value Inputs, Level 3 [Member] | Money Market Funds [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value
Total

[1] The change in the fair value of the common stock warrant and convertible notes payable for the three months ended March 31, 2019 was recorded as a decrease to other income (expense) and interest expense of $5, in the statements of operations and comprehensive loss.