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Shareholders' Equity - Schedule of Shares Granted and Vested (Details) - Share Award Plans - $ / shares | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Number of Shares |  |  |
Unvested shares at the beginning of the year (in shares) | 227,340 | 161,990 | 148,010
Shares awarded (in shares) | 420,000 | 202,500 | 123,800
Shares vested/forfeited (in shares) | (212,790) | (137,150) | (109,820)
Unvested shares at the end of the year (in shares) | 434,550 | 227,340 | 161,990
Weighted Average Award Date Fair Value |  |  |
Unvested shares at the beginning of the year (in dollars per share) | $ 12.52 | $ 19.41 | $ 19.71
Shares awarded (in dollars per share) | 3.65 | 8.65 | 18.72
Shares vested/forfeited (in dollars per share) | 7.04 | 8.94 | 18.31
Unvested shares at the end of the year (in dollars per share) | $ 6.15 | $ 12.52 | $ 19.41

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- Definition Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested Or Forfeited in Period + References No definition available. + Details
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- Definition Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested Or Forfeited in Period, Weighted Average Grant Date Fair Value + References No definition available. + Details
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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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