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Earnings per Ordinary Share - Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Class of Stock [Line Items] |  |  |  |  |
Net income/(loss) |  | $ (15.1) | $ (253.8) | $ 1.0 | $ (81.5)
Preference share dividends |  | (7.6) | (7.7) | (22.8) | (28.7)
Change in redemption value |  | 0.0 | (5.6) | 0.0 | (8.0)
Proportion due to non-controlling interest |  | 0.1 | (0.6) | (0.2) | (0.8)
Basic and diluted net (loss) available to ordinary shareholders (2) |  | (22.6) | (267.7) | (22.0) | (119.0)
Diluted net income available to ordinary shareholders |  | $ (22.6) | $ (267.7) | $ (22.0) | $ (119.0)
Ordinary shares: |  |  |  |  |
Basic weighted average ordinary shares |  | 59,692,623 | 59,759,730 | 59,637,361 | 59,862,540
Weighted average effect of dilutive securities |  | 0 | 0 | 0 | 0
Total diluted weighted average ordinary shares |  | 59,692,623 | 59,759,730 | 59,637,361 | 59,862,540
(Loss)/earnings per ordinary share: |  |  |  |  |
Basic (in usd per share) |  | $ (0.38) | $ (4.48) | $ (0.37) | $ (1.99)
Diluted (in usd per share) |  | $ (0.38) | $ (4.48) | $ (0.37) | $ (1.99)
7.401% preference shares |  |  |  |  |
(Loss)/earnings per ordinary share: |  |  |  |  |
Preference shares, rate |  |  |  | 7.401% |
7.250% preference shares |  |  |  |  |
(Loss)/earnings per ordinary share: |  |  |  |  |
Preference shares, rate |  |  |  | 7.25% |
Additional paid-in capital | Redemption costs of preference shares |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |
Change in redemption value | [1] |  |  | $ 0.0 | $ 8.0
(Loss)/earnings per ordinary share: |  |  |  |  |
Stock Redeemed or Called During Period, Value |  |  |  | $ 0.0 | $ 293.2
[1] | The $8.0 million deduction from net income in 2017 is attributable to the reclassification from additional paid-in capital to retained earnings representing the difference between the capital raised upon issuance of the 7.401% and 7.250% Perpetual Non-Cumulative Preference Shares, net of issuance costs, and the final redemption costs of $293.2 million.

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