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Shareholders' Equity - Preferred shares (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions |  |  | 1 Months Ended | 4 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | --- | ---
Jan. 01, 2018 | Sep. 29, 2016 | Nov. 30, 2017 | Aug. 31, 2017 | Nov. 30, 2017 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Jan. 02, 2018
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Preferred shares, par value per share |  |  |  |  |  | $ 0.01 |  |  |
Average cost per share |  |  |  |  |  | $ 29.29 | $ 25.96 | $ 26.78 |
Redemption of preferred shares |  |  |  |  |  | $ 0 | $ 0 | $ 92,555 |
Series C Preferred Shares |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Preferred shares, dividend rate (as a percent) | 6.75% |  |  |  |  |  |  |  |
Preferred shares, redemption price per share |  |  |  |  |  |  |  |  | $ 25
Series E preferred shares |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Non-cumulative preferred shares |  | $ 450,000 |  |  |  |  |  |  |
Preferred shares, dividend rate (as a percent) |  | 5.25% |  |  |  |  |  |  |
Preferred shares, par value per share |  | $ 0.01 |  |  |  |  |  |  |
Liquidation preference per share |  | 25,000 |  |  |  |  |  |  |
Preferred shares, redemption price per share |  | $ 25,000 |  |  |  |  |  |  |
Series E depositary share equivalent |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Preference shares, number of shares issued |  | 18.0 |  |  |  |  |  |  |
Proportionate interest of preference shares, per depositary share |  | 0.10% |  |  |  |  |  |  |
Liquidation preference per share |  | $ 25 |  |  |  |  |  |  |
Preferred shares, redemption price per share |  | $ 25 |  |  |  |  |  |  |
Series F Preferred Shares |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Preferred shares issued |  |  | $ 100,000 | $ 230,000 | $ 330,000 |  |  |  |
Preferred shares, dividend rate (as a percent) |  |  |  |  | 5.45% |  |  |  |
Preferred shares, par value per share |  |  | $ 0.01 |  | $ 0.01 |  |  |  |
Liquidation preference per share |  |  | 25,000 |  | 25,000 |  |  |  |
Preferred shares, redemption price per share |  |  | $ 25,000 |  | $ 25,000 |  |  |  |
Series F depositary share equivalent |  |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |  |
Preference shares, number of shares issued |  |  | 13.2 |  | 13.2 |  |  |  |
Proportionate interest of preference shares, per depositary share |  |  | 0.10% |  | 0.10% |  |  |  |
Liquidation preference per share |  |  | $ 25 |  | $ 25 |  |  |  |
Preferred shares, redemption price per share |  |  | $ 25 |  | $ 25 |  |  |  |

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- Definition The cash outflow to reacquire preferred stock during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585 + Details
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- Definition The per share liquidation preference (or restrictions) of nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(d)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21484-112644 + Details
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