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Capital Structure - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands |  |  | 12 Months Ended |
--- | --- | --- | --- | ---
Aug. 13, 2019 | Sep. 20, 2016 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | May 02, 2013
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Additional paid in capital |  |  | $ 1,469,700 |  | $ 1,201,700 |  |  |
Aggregate liquidation preferences |  |  | 775,000 |  | 775,000 |  |  |
Preferred stock issuance cost |  |  | 21,500 |  | 21,500 |  |  |
Authorized share capital |  |  | $ 745 |  | $ 745 |  |  |
Number of ordinary shares |  |  | 70,000,000 |  | 70,000,000 |  |  |
Ordinary shares, par value |  |  | $ 0.01 |  | $ 0.01 |  |  |
Number of preference shares |  |  | 30,000,000 |  | 30,000,000 |  |  |
Preference shares, par value |  |  | $ 0.0015144558 |  |  |  |  |
Ordinary shares, issued |  |  | 60,395,839 |  | 60,395,839 |  |  |
Preferred Stock, Redemption Amount |  |  |  |  |  |  |  | $ 275,000
Preference shares liquidation preference, value | $ 250,000 |  |  |  |  |  |  |
Capital contribution (1) |  |  | $ 268,000 | [1] | $ 0 | $ 0 |  |
5.950% Preference Shares (AHL PRC) |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Preference shares, par value |  |  | $ 0.0015144558 |  | $ 0.0015144558 |  |  |
Preference shares, issued |  |  | 11,000,000 |  | 11,000,000 |  |  | 11,000,000
Preference shares, rate |  |  | 5.95% |  | 5.95% |  |  |
Redemption price per share |  |  | $ 25 |  | $ 25 |  |  | $ 25
5.625% Preference Shares (AHL PRD) |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Preferred stock issuance cost |  |  |  |  |  |  | $ 8,700 |
Preference shares, par value |  |  | $ 0.0015144558 |  | $ 0.0015144558 |  |  |
Preference shares, issued |  |  | 10,000,000 |  | 10,000,000 |  |  |
Preference shares, rate |  | 5.625% | 5.625% |  | 5.625% |  |  |
Redemption price per share |  | $ 25 | $ 25 |  | $ 25 |  |  |
Proceeds or share issuance |  | $ 241,300 |  |  |  |  |  |
Preference shares liquidation preference, value |  |  |  |  |  |  | $ 250,000 |
5.625% Preference Shares, rep by Dep Shares (AHL PRE) |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Preferred stock issuance cost | $ 8,400 |  |  |  |  |  |  |
Preference shares, par value |  |  | $ 0.0015144558 |  | $ 0.0015144558 |  |  |
Preference shares, issued | 10,000,000 |  | 10,000,000 |  | 10,000,000 |  |  |
Preference shares, rate | 5.625% |  | 5.625% |  | 5.625% |  |  |
Redemption price per share | $ 25 |  | $ 25 |  | $ 25 |  |  |
Additional paid-in capital | Preference Shares |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Proceeds or share issuance | $ 241,600 |  | $ 0 |  | $ 241,600 | $ 0 |  |
[1] | The $268.0 million relates to additional capital contribution received from our parent company Highlands Bermuda Holdco, Ltd.

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