Fair Value Measurements - Warrant Valuation Assumptions (Details) - Liabilities - Common stock warrants - Option pricing model	Dec. 31, 2018 Y item	Dec. 31, 2017 Y item
Significant assumptions used in valuation of the Company's warrants
Life of treasury bonds	1 year	2 years
Volatility
Significant assumptions used in valuation of the Company's warrants
Warrants, Measurement Input	0.700	0.700
Risk free interest rate
Significant assumptions used in valuation of the Company's warrants
Warrants, Measurement Input	0.0257	0.0189
Strike price
Significant assumptions used in valuation of the Company's warrants
Warrants, Measurement Input	6.00	6.00
Share price
Significant assumptions used in valuation of the Company's warrants
Warrants, Measurement Input	0.58	2.69
Expected life
Significant assumptions used in valuation of the Company's warrants
Warrants, Measurement Input | Y	1	2