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Basis of Presentation and New Accounting Standards (Details) $ / shares in Units, $ in Thousands |  |  |  |  | 6 Months Ended |  |  |
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Aug. 05, 2019 $ / shares shares | Apr. 25, 2019 USD ($) | Apr. 24, 2019 USD ($) | May 23, 2018 $ / shares shares | Jun. 30, 2019 USD ($) $ / shares shares | Jun. 30, 2018 USD ($) | Aug. 06, 2019 shares | Dec. 31, 2018 $ / shares shares | May 24, 2018 shares
Basis Of Presentation And New Accounting Standards [Line Items] |  |  |  |  |  |  |  |  |
Cash proceeds from sale of subsidiary | $ |  |  |  |  | $ 2,789 | $ 0 |  |  |
Reverse stock split of common stock |  |  |  | 0.1 |  |  |  |  |
Common stock, par value (in dollars per share) | $ / shares |  |  |  | $ 0.001 | $ 0.001 |  |  | $ 0.001 |
Common stock, shares authorized (in shares) |  |  |  | 75,000,000 | 100,000,000 |  |  | 100,000,000 | 100,000,000
Common stock, shares issued (in shares) |  |  |  | 61,600,000 | 443,117 |  |  | 443,117 | 6,200,000
Common stock, shares outstanding (in shares) |  |  |  | 61,600,000 | 296,609 |  |  | 296,609 | 6,200,000
Number of shares callable by warrants (in shares) |  |  |  | 23,400,000 |  |  |  |  | 2,300,000
Preferred stock, shares authorized (in shares) |  |  |  | 5,000,000 | 5,000,000 |  |  | 5,000,000 | 5,000,000
Common stock, reverse stock split, fractional shares issued |  |  |  | 0 |  |  |  |  |
Operating lease right-of-use assets | $ |  |  |  |  | $ 905 |  |  |  |
Operating lease, liability | $ |  |  |  |  | $ 905 |  |  |  |
Subsequent Event [Member] |  |  |  |  |  |  |  |  |
Basis Of Presentation And New Accounting Standards [Line Items] |  |  |  |  |  |  |  |  |
Reverse stock split of common stock | 0.02 |  |  |  |  |  |  |  |
Common stock, par value (in dollars per share) | $ / shares | $ 0.001 |  |  |  |  |  |  |  |
Preferred stock, shares authorized (in shares) | 5,000,000 |  |  |  |  |  | 5,000,000 |  |
Common stock, reverse stock split, fractional shares issued | 0 |  |  |  |  |  |  |  |
Reverse stock split effective date for trading purposes | Aug. 06, 2019 |  |  |  |  |  |  |  |
Reverse stock split of common stock description | Upon effectiveness, each 50 shares of issued and outstanding Common Stock were converted into one newly issued and outstanding share of Common Stock. |  |  |  |  |  |  |  |
2014 Equity Incentive Plan [Member] |  |  |  |  |  |  |  |  |
Basis Of Presentation And New Accounting Standards [Line Items] |  |  |  |  |  |  |  |  |
Number of shares callable by warrants (in shares) |  |  |  | 9,100,000 |  |  |  |  | 900,000
Sale of UK Subsidiary and Certain Assets [Member] | Loan and Security Agreement [Member] |  |  |  |  |  |  |  |  |
Basis Of Presentation And New Accounting Standards [Line Items] |  |  |  |  |  |  |  |  |
Cash proceeds from sale of subsidiary | $ |  |  | $ 4,000 |  |  |  |  |  |
Payments for principal, interest and fees | $ |  |  | $ 1,700 |  |  |  |  |  |
Sale of the Japanese Subsidiary and Certain Assets [Member] | Loan and Security Agreement [Member] |  |  |  |  |  |  |  |  |
Basis Of Presentation And New Accounting Standards [Line Items] |  |  |  |  |  |  |  |  |
Cash proceeds from sale of subsidiary | $ |  | $ 3,000 |  |  |  |  |  |  |
Payments for principal, interest and fees | $ |  | $ 1,400 |  |  |  |  |  |  |

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