Balance Sheet Account Detail (Fair Value Measurements) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	$ 6,035	$ 4,012
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingently issuable common stock	2,000	2,200
Derivative liabilities	6,035	4,012
Total financial liabilities	8,035	6,212
Level 1 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingently issuable common stock	0	0
Derivative liabilities	0	0
Total financial liabilities	0	0
Level 2 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingently issuable common stock	0	0
Derivative liabilities	0	0
Total financial liabilities	0	0
Level 3 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingently issuable common stock	2,000	2,200
Derivative liabilities	6,035	4,012
Total financial liabilities	$ 8,035	$ 6,212