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Share-Based Compensation - Restricted Stock (Details) - USD ($) $ / shares in Units, $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Restricted Stock |  |  |
Unvested restricted stock |  |  |
Outstanding at the beginning of the period (in shares)) | 98,000 |  |
Granted (in shares) | 4,000 |  |
Vested (in shares) | (45,000) |  |
Forfeited (in shares) | (8,000) |  |
Outstanding at the end of the period (in shares) | 49,000 | 98,000 |
Weighted-Average Grant-Date Fair Value |  |  |
Outstanding at the beginning of the period (in dollars per share) | $ 270.27 |  |
Granted (in dollars per share) | 35.27 |  |
Vested (in dollars per share) | 298.17 |  |
Forfeited (in dollars per share) | 262.06 |  |
Outstanding at the end of the period (in dollars per share) | $ 226.06 | $ 270.27 |
Total future compensation cost related to unvested awards that are expected to vest | $ 6.8 |  |
Weighted Average Period for Cost recognition | 2 years |  |
Restricted Stock | Employees and Director |  |  |
Unvested restricted stock |  |  |
Granted (in shares) | 4,156 | 65,299 | 47,850
Restricted Stock | Maximum |  |  |
Weighted-Average Grant-Date Fair Value |  |  |
Vesting period of shares | 5 years |  |
Restricted Stock | Maximum | Employees and Director |  |  |
Weighted-Average Grant-Date Fair Value |  |  |
Vesting period of shares | 4 years | 4 years | 4 years
Restricted Stock Based on Performance Conditions | Certain Executive Officers |  |  |
Unvested restricted stock |  |  |
Granted (in shares) | 31,204 |  |
Weighted-Average Grant-Date Fair Value |  |  |
Vesting period of shares | 3 years |  |
Restricted Stock Based on Performance Conditions | Executive Officers |  |  |
Unvested restricted stock |  |  |
Outstanding at the beginning of the period (in shares)) | 65,000 |  |
Granted (in shares) | 59,490 | 48,253 | 20,199
Vested (in shares) | (26,000) |  |
Outstanding at the end of the period (in shares) | 98,000 | 65,000 |
Weighted-Average Grant-Date Fair Value |  |  |
Outstanding at the beginning of the period (in dollars per share) | $ 223.39 |  |
Granted (in dollars per share) | 148.00 |  |
Vested (in dollars per share) | 276.85 |  |
Outstanding at the end of the period (in dollars per share) | $ 163.74 | $ 223.39 |
Vesting period of shares | 3 years | 3 years | 3 years
Restricted Stock Based on Market Conditions |  |  |
Unvested restricted stock |  |  |
Outstanding at the beginning of the period (in shares)) | 64,000 |  |
Granted (in shares) | 22,931 | 52,191 | 21,163
Vested (in shares) | (3,000) |  |
Forfeited (in shares) | (5,000) |  |
Outstanding at the end of the period (in shares) | 79,000 | 64,000 |
Weighted-Average Grant-Date Fair Value |  |  |
Outstanding at the beginning of the period (in dollars per share) | $ 142.00 |  |
Granted (in dollars per share) | 111.00 |  |
Vested (in dollars per share) | 558.12 |  |
Forfeited (in dollars per share) | 558.12 |  |
Outstanding at the end of the period (in dollars per share) | $ 91.34 | $ 142.00 |
Total future compensation cost related to unvested awards that are expected to vest | $ 2.9 |  |
Weighted Average Period for Cost recognition | 1 year 6 months 29 days |  |
Vesting period of shares | 3 years | 3 years | 3 years
Restricted Stock Units | Executive Officers |  |  |
Unvested restricted stock |  |  |
Granted (in shares) | 31,000 |  |
Outstanding at the end of the period (in shares) | 31,000 |  |
Weighted-Average Grant-Date Fair Value |  |  |
Granted (in dollars per share) | $ 148.00 |  |
Outstanding at the end of the period (in dollars per share) | $ 148.00 |  |

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- Definition Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + 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 (i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Amount of cost to be recognized for 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 (i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition. + 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 (a)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. + 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)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event. + 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)(3) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + 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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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period. + 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)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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