Basis of Presentation and Significant Accounting Policies - Summary of Fair Values of Assets and Liabilities Measured at Fair Value on Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Cash and restricted cash	$ 2,752	$ 777
Total assets	2,752	777
Warrants potentially settleable in cash	263	569
Total liabilities	263	569
Quoted Prices in Active Markets Level 1 [Member]
Cash and restricted cash	2,752	777
Total assets	2,752	777
Warrants potentially settleable in cash
Total liabilities
Significant Other Observable Inputs Level 2 [Member]
Cash and restricted cash
Total assets
Warrants potentially settleable in cash
Total liabilities
Unobservable Inputs Level 3 [Member]
Cash and restricted cash
Total assets
Warrants potentially settleable in cash	263	569
Total liabilities	$ 263	$ 569