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Incentive Plans (Summary of Additional Stock Option Information) (Details) | 12 Months Ended
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Dec. 31, 2015 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Options outstanding | shares | 465,756
Options outstanding, average remaining life (in years) | 4 years 6 months 18 days
Options outstanding, aggregate intrinsic value | $ | $ 9,311,711
Options exercisable | shares | 127,077
Options exercisable, average remaining life (in years) | 3 years 8 months 23 days
Options exercisable, aggregate intrinsic value | $ | $ 3,053,997
$32.53 to $37.06 [Member] |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Lower range limit of exercise price (in dollars per share) | $ / shares | $ 32.53
Upper range limit of exercise price (in dollars per share) | $ / shares | $ 37.06
Options outstanding | shares | 171,592
Options outstanding, average remaining life (in years) | 3 years 10 months 20 days
Options outstanding, aggregate intrinsic value | $ | $ 4,614,797
Options exercisable | shares | 62,213
Options exercisable, average remaining life (in years) | 3 years 6 months 12 days
Options exercisable, aggregate intrinsic value | $ | $ 1,707,361
$37.07 to $39.45 [Member] |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Lower range limit of exercise price (in dollars per share) | $ / shares | $ 37.07
Upper range limit of exercise price (in dollars per share) | $ / shares | $ 39.45
Options outstanding | shares | 5,615
Options outstanding, average remaining life (in years) | 2 years 2 days
Options outstanding, aggregate intrinsic value | $ | $ 132,891
Options exercisable | shares | 5,615
Options exercisable, average remaining life (in years) | 2 years 2 days
Options exercisable, aggregate intrinsic value | $ | $ 132,891
$39.46 to $40.25 [Member] |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Lower range limit of exercise price (in dollars per share) | $ / shares | $ 39.46
Upper range limit of exercise price (in dollars per share) | $ / shares | $ 40.25
Options outstanding | shares | 218,899
Options outstanding, average remaining life (in years) | 4 years 7 months 14 days
Options outstanding, aggregate intrinsic value | $ | $ 4,564,023
Options exercisable | shares | 59,249
Options exercisable, average remaining life (in years) | 4 years 1 month 5 days
Options exercisable, aggregate intrinsic value | $ | $ 1,213,745
$40.26 to $70.57 [Member] |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Lower range limit of exercise price (in dollars per share) | $ / shares | $ 40.26
Upper range limit of exercise price (in dollars per share) | $ / shares | $ 70.57
Options outstanding | shares | 69,650
Options outstanding, average remaining life (in years) | 6 years 1 month 13 days
Options outstanding, aggregate intrinsic value | $ | $ 0
Options exercisable | shares | 0
Options exercisable, average remaining life (in years) | 0 years
Options exercisable, aggregate intrinsic value | $ | $ 0

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- Definition Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=6415400&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://www.xbrl.org/2003/role/presentationRef -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=6415400&loc=d3e5070-113901 + Details
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