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Variable Interest Entity and Noncontrolling Interests - Non-redeemable noncontrolling interest (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Noncontrolling Interest [Line Items] |  |  |  |
Non-redeemable noncontrolling interest, beginning of year |  | $ 762,777 | $ 791,560 |
Amounts attributable to nonredeemable noncontrolling interests |  | (53,076) | (40,072) | $ 48,507
Other Amounts Attributable to Noncontrolling Interests |  | (375) | 0 |
Non-redeemable noncontrolling interest, end of year |  | 823,007 | 762,777 | 791,560
Watford Holdings Ltd | Noncontrolling Interest |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |
Non-redeemable noncontrolling interest, beginning of year |  | 762,777 | 791,560 |
Additional paid in capital attributable to noncontrolling interests |  | 1,334 | (2,929) |
Repurchases attributable to non-redeemable noncontrolling interests (1) | [1] | (2,867) | (75,056) |
Amounts attributable to nonredeemable noncontrolling interests |  | 53,076 | 40,072 |
Other comprehensive (income) loss attributable to noncontrolling interests |  | 9,062 | 9,130 |
Non-redeemable noncontrolling interest, end of year |  | $ 823,007 | $ 762,777 | $ 791,560
Common shares | Watford Holdings Ltd | Noncontrolling Interest | Noncontrolling Ownership [Member] |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |
Noncontrolling interest, ownership percentage by noncontrolling owners |  | 87.00% |  |
[1] | During 2020 and 2019, Watford’s board of directors authorized the investment in Watford’s common shares through a share repurchase program

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