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Debt - January 2017 Exchangeable Senior Notes - Additional Information (Detail) |  |  | 1 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Jan. 20, 2017 USD ($) d $ / shares | Jan. 19, 2017 $ / shares | Oct. 31, 2018 USD ($) shares | Dec. 31, 2018 USD ($) shares | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($)
Debt Disclosure [Line Items] |  |  |  |  |  |
Convertible senior notes, exchanged |  |  |  | $ 29,490,000 |  | $ 128,115,000
Carrying amount of debt conversion option |  |  |  | 29,369,000 |  | 127,436,000
Transaction costs |  |  |  | 121,000 |  | 680,000
Interest expense, non-cash |  |  |  | 2,183,000 | $ 2,332,000 | 7,783,000
Common Shares |  |  |  |  |  |
Debt Disclosure [Line Items] |  |  |  |  |  |
Carrying amount of debt conversion option |  |  |  | 5,011,000 |  | $ 40,062,000
Convertible Debt | 2017 Notes |  |  |  |  |  |
Debt Disclosure [Line Items] |  |  |  |  |  |
Convertible senior notes, principal amount | $ 30,000,000 |  |  |  |  |
Convertible senior notes, exchanged |  |  | $ 30,000,000 |  |  |
Convertible senior notes, stated interest rate | 3.50% |  |  |  |  |
Convertible senior notes, due date | 2047 |  |  |  |  |
Convertible senior notes, repurchase price at option of the issuer | 100.00% |  |  |  |  |
Net proceeds from offering | $ 28,800,000 |  |  |  |  |
Convertible senior notes, outstanding amount |  |  |  | $ 0 |  |
Convertible senior notes redemption, end date | Jan. 15, 2047 |  |  |  |  |
Convertible senior notes, mandatory exchange in whole or in part if daily VWAP equaled or exceeded percentage of exchange price | 130.00% |  |  |  |  |
Convertible senior notes, mandatory exchange in whole or in part if daily VWAP, stock trigger price | $ / shares | $ 5.05 |  |  |  |  |
Convertible senior notes, mandatory exchange in whole or in part if daily VWAP equaled or exceeded percentage of exchange price, at least number of VWAP Trading days | d | 20 |  |  |  |  |
Convertible senior notes, mandatory exchange in whole or in part if daily VWAP equaled or exceeded percentage of exchange price, in any number of VWAP Trading days | d | 30 |  |  |  |  |
Convertible senior notes, percentage of premium initial exchange price |  | 35.00% |  |  |  |
Convertible senior notes, total ADS into which the debt is exchangeable | shares |  |  |  | 0 |  |
Convertible senior notes, carrying value, exchanged |  |  | 29,200,000 |  |  |
Equity component of convertible notes issuance cost |  |  | 24,400,000 |  |  |
Debt instrument increase accrued interest |  |  | 300,000 |  |  |
Convertible senior notes, interest payable dates |  |  |  | payable semi-annually in arrears on January 15 and July 15 of each year, beginning on July 15, 2017 |  |
Convertible senior notes, payment start date | Jul. 15, 2017 |  |  |  |  |
Convertible senior notes, maturity date | Jan. 15, 2047 |  |  |  |  |
Convertible senior notes, discount | $ 1,200,000 |  |  | $ 0 | 1,000,000 |
Convertible notes, carrying amount net of unamortized discount |  |  |  |  | 29,000,000 |
Convertible notes, interest expense |  |  |  | 1,100,000 | 1,200,000 |
Interest expense, contractual coupon interest |  |  |  | 900,000 | 1,000,000 |
Accrued interest on convertible note |  |  |  |  | 500,000 |
Interest payments on notes |  |  |  | 1,100,000 | 500,000 |
Convertible Debt | 2017 Notes | Non Cash |  |  |  |  |  |
Debt Disclosure [Line Items] |  |  |  |  |  |
Interest expense, non-cash |  |  |  | $ 200,000 | $ 200,000 |
Convertible Debt | 2017 Notes | Common Shares |  |  |  |  |  |
Debt Disclosure [Line Items] |  |  |  |  |  |
Carrying amount of debt conversion option |  |  | $ 5,000,000 |  |  |
Convertible Debt | 2017 Notes | American Depositary Shares |  |  |  |  |  |
Debt Disclosure [Line Items] |  |  |  |  |  |
Convertible senior notes, exchange rate of ADS per $1,000 principal amount of notes | 257.2016 |  | 257.2016 |  |  |
Convertible senior notes, initial exchange price | $ / shares | $ 3.89 | $ 2.88 |  |  |  |
Convertible senior notes, total ADS into which the debt is exchangeable | shares |  |  | 7,716,046 |  |  |
Transaction costs |  |  | $ 100,000 |  |  |

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- Definition The net amount of stock issued during the period upon the conversion of convertible securities, net of adjustments (for example, to additional paid in capital) including the write-off of an equity component recognized to record the convertible debt instrument as two separate components - a debt component and an equity component. This item is meant to disclose the value of shares issued on conversion of convertible securities that were recorded as two separate (debt and equity) components. + References No definition available. + Details
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- Details
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- Details
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- Details
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