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Incentive Plans (Summary of Additional Stock Option Information) (Details) | 12 Months Ended
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Dec. 31, 2020 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Options outstanding (in shares) | 322,700
Options outstanding, average remaining life (in years) | 4 years 7 months 6 days
Options exercisable (in shares) | 110,700
Options exercisable, average remaining life (in years) | 3 years 3 months 18 days
$50.00 to $59.99 |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Lower range limit of exercise price (in dollars per share) | $ / shares | $ 50.00
Upper range limit of exercise price (in dollars per share) | $ / shares | $ 59.99
Options outstanding (in shares) | 7,300
Options outstanding, average remaining life (in years) | 2 years 1 month 6 days
Options exercisable (in shares) | 7,300
Options exercisable, average remaining life (in years) | 2 years 1 month 6 days
$60.00 to $69.99 |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Lower range limit of exercise price (in dollars per share) | $ / shares | $ 60.00
Upper range limit of exercise price (in dollars per share) | $ / shares | $ 69.99
Options outstanding (in shares) | 69,500
Options outstanding, average remaining life (in years) | 3 years 1 month 6 days
Options exercisable (in shares) | 69,500
Options exercisable, average remaining life (in years) | 3 years 1 month 6 days
$70.00 to $79.99 |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Lower range limit of exercise price (in dollars per share) | $ / shares | $ 70.00
Upper range limit of exercise price (in dollars per share) | $ / shares | $ 79.99
Options outstanding (in shares) | 166,700
Options outstanding, average remaining life (in years) | 4 years 7 months 6 days
Options exercisable (in shares) | 33,900
Options exercisable, average remaining life (in years) | 3 years 10 months 24 days
$80.00 to $89.99 |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Lower range limit of exercise price (in dollars per share) | $ / shares | $ 80.00
Upper range limit of exercise price (in dollars per share) | $ / shares | $ 89.99
Options outstanding (in shares) | 3,600
Options outstanding, average remaining life (in years) | 6 years 2 months 12 days
Options exercisable (in shares) | 0
Options exercisable, average remaining life (in years) |
$100.00 to $109.99 |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Lower range limit of exercise price (in dollars per share) | $ / shares | $ 100.00
Upper range limit of exercise price (in dollars per share) | $ / shares | $ 109.99
Options outstanding (in shares) | 75,600
Options outstanding, average remaining life (in years) | 6 years 1 month 6 days
Options exercisable (in shares) | 0
Options exercisable, average remaining life (in years) |

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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=120381028&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=120381028&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=120381028&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=120381028&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term of exercisable stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the 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 (e)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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