Fair Value Measurements (Details) - USD ($) $ in Thousands		Mar. 31, 2017	Dec. 31, 2016
Financial Assets:
Held-to-maturity Securities, Fair Value		$ 2,961
Fixed Income Securities [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value		1,314
Fair Value, Measurements, Recurring [Member]
Financial Assets:
Assets, Fair Value Disclosure		3,004
Financial Liabilities:
Common stock warrant liability	[1]	60	$ 69
Financial Liabilities Fair Value Disclosure		60	69
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value		2,961
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Assets, Fair Value Disclosure		43
Financial Liabilities:
Common stock warrant liability	[1]	0	0
Financial Liabilities Fair Value Disclosure		0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Assets, Fair Value Disclosure		2,961
Financial Liabilities:
Common stock warrant liability	[1]	0	0
Financial Liabilities Fair Value Disclosure		0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value		2,961
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Assets, Fair Value Disclosure		0
Financial Liabilities:
Common stock warrant liability	[1]	60	69
Financial Liabilities Fair Value Disclosure		60	$ 69
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value		0
Money Market Funds [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value		43
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value		43
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value		0
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Financial Assets:
Held-to-maturity Securities, Fair Value		$ 0

[1] The change in the fair value of the common stock warrant and convertible notes payable for the three months ended March 31, 2017 was recorded as a decrease to other income (expense) and interest expense of $9, in the statements of operations and comprehensive loss.