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Net Income Per Share - Additional Information (Detail) $ / shares in Units, $ in Millions | 12 Months Ended | 66 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2020 USD ($) $ / shares shares | Dec. 31, 2019 $ / shares shares | Dec. 31, 2018 shares | Dec. 31, 2020 USD ($) $ / shares shares | Aug. 03, 2018 $ / shares | Nov. 02, 2016 USD ($) | Jun. 30, 2015 USD ($) | May 01, 2013 $ / shares | Apr. 30, 2013 $ / shares
Schedule Of Earnings Per Share [Line Items] |  |  |  |  |  |  |  |  |
Common Stock, Shares, Outstanding | 45,809,139 |  |  | 45,809,139 |  |  |  |  |
Class of Warrant or Right, Outstanding | 4,877,749 |  |  | 4,877,749 |  |  |  |  |
Number of new common stock issued | 45,865,081 | 45,571,743 |  | 45,865,081 |  |  |  |  |
Common Stock, Par or Stated Value Per Share | $ / shares | $ 0.01 | $ 0.01 |  | $ 0.01 |  |  |  |  | $ 0.01
Exercise price of common stock | $ / shares |  |  |  |  |  |  |  | $ 16.67 |
Warrant exercised | 34 | 0 | 194 |  |  |  |  |  |
Stock Issued During Period, Shares, New Issues | 8 | 0 | 194 |  |  |  |  |  |
First Warrant Buyback Authorization Dollars | $ |  |  |  |  |  |  | $ 10 |  |
Payments for Repurchase of Warrants | $ |  |  |  | $ 8 |  |  |  |  |
Warrants Repurchased Average Cost per Warrant | $ / shares |  |  |  | $ 8.21 |  |  |  |  |
SecondWarrantBuyBackAuthorizedDollars | $ |  |  |  |  |  | $ 10 |  |  |
Warrants Purchased Shares |  |  |  | 985,331 |  |  |  |  |
RemainingWarrantBuyBackAuthorizedDollars | $ | $ 12 |  |  | $ 12 |  |  |  |  |
AMPS Exchange Total Warrants Issued |  |  |  |  | 824,307 |  |  |  |
AMPS Exchange Total Warrants Issued Cost Per Share | $ / shares |  |  |  |  | $ 9.72 |  |  |  |

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