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Shareholders' Equity - Share repurchase program (Details) - USD ($) $ / shares in Units, $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Class of Stock [Line Items] |  |  |
Treasury stock, value of shares acquired | $ 83,472 | $ 2,871 | $ 282,762
Treasury stock, shares acquired (shares) | 2,850,102 | 110,598 | 10,559,850
Treasury stock, average cost per share | $ 29.29 | $ 25.96 | $ 26.78
Common shares held in treasury (shares) | 172,280,199 | 168,997,994 | 168,282,449
Common shares held in treasury, at cost | $ 2,500,000 |  |
Common shares |  |  |
Class of Stock [Line Items] |  |  |
Remaining share repurchase authorization | $ 916,500 |  |
Cumulative number of shares acquired since inception of share repurchase program | 389,200,000 |  |
Aggregate purchase price of shares acquired since inception of share repurchase program | $ 4,100,000 |  |

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- Definition Aggregate cumulative purchase price of common and preferred stock that have been repurchased since the inception of the share repurchase program. + References No definition available. + Details
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- Definition Amount remaining of a stock repurchase plan authorized. + References No definition available. + Details
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- Definition Total cost of shares repurchased divided by the total number of shares repurchased. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655 + Details
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- Definition Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29,30) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655 + Details
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