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Stock Options (Schedule of Qualified Stock Options Outstanding and Exercisable) (Details) - Qualified Stock Options - $ / shares | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Options Outstanding (in shares) | 140,170 | 172,875 | 220,820 | 254,195
Options Exercisable (in shares) | 96,320 | 111,875 | 136,220 |
$11.45 - $22.55 |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Range of Exercise Price, Lower Range Limit (in dollars per share) | $ 11.45 |  |  |
Range of Exercise Price, Upper Range Limit (in dollars per share) | $ 22.55 |  |  |
Options Outstanding, Exercise price range (in shares) | 6,000 |  |  |
Options Outstanding, Remaining Contractual Life | 6 months 10 days |  |  |
Options, Outstanding, Exercise Price (in dollars per share) | $ 13.66 |  |  |
Options Exercisable, Exercise price range (in shares) | 6,000 |  |  |
Options Exercisable, Exercise Price (in dollars per share) | $ 13.66 |  |  |
$24.69 - $42.70 |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Range of Exercise Price, Lower Range Limit (in dollars per share) | 24.69 |  |  |
Range of Exercise Price, Upper Range Limit (in dollars per share) | $ 42.70 |  |  |
Options Outstanding, Exercise price range (in shares) | 54,520 |  |  |
Options Outstanding, Remaining Contractual Life | 3 years 6 months 29 days |  |  |
Options, Outstanding, Exercise Price (in dollars per share) | $ 35.83 |  |  |
Options Exercisable, Exercise price range (in shares) | 54,520 |  |  |
Options Exercisable, Exercise Price (in dollars per share) | $ 35.83 |  |  |
$49.44 - $83.99 |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Range of Exercise Price, Lower Range Limit (in dollars per share) | 49.44 |  |  |
Range of Exercise Price, Upper Range Limit (in dollars per share) | $ 83.99 |  |  |
Options Outstanding, Exercise price range (in shares) | 70,150 |  |  |
Options Outstanding, Remaining Contractual Life | 6 years 6 months 21 days |  |  |
Options, Outstanding, Exercise Price (in dollars per share) | $ 57.92 |  |  |
Options Exercisable, Exercise price range (in shares) | 35,800 |  |  |
Options Exercisable, Exercise Price (in dollars per share) | $ 54.96 |  |  |
$92.50 - $92.50 |  |  |  |
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] |  |  |  |
Range of Exercise Price, Lower Range Limit (in dollars per share) | 92.50 |  |  |
Range of Exercise Price, Upper Range Limit (in dollars per share) | $ 92.50 |  |  |
Options Outstanding, Exercise price range (in shares) | 9,500 |  |  |
Options Outstanding, Remaining Contractual Life | 9 years 4 months 9 days |  |  |
Options, Outstanding, Exercise Price (in dollars per share) | $ 92.50 |  |  |
Options Exercisable, Exercise price range (in shares) | 0 |  |  |
Options Exercisable, Exercise Price (in dollars per share) | $ 0 |  |  |

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- Definition The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option 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)(1)(iii) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Number of options outstanding, including both vested and non-vested 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 -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 Reference 2: 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)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range. + 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 (g) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The number of shares reserved for issuance pertaining to the outstanding exercisable stock options as of the balance sheet date in the customized range of exercise prices for which the market and performance vesting condition has been satisfied. + 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)(iii) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices. + 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)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range. + 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 (g) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Weighted average exercise price as of the balance sheet date for those equity-based payment arrangements exercisable and outstanding. + 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)(iii) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The weighted average price as of the balance sheet date at which grantees could acquire the underlying shares with respect to all outstanding stock options which are in the customized range of exercise prices. + 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)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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