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Incentive Plans (Tables) | 3 Months Ended
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Mar. 31, 2018
Incentive Plans [Abstract] |
Share-Based Plans, Amounts Recognized |
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﻿ | Three Months Ended
﻿ | March 31,
﻿(Thousands of dollars) |  | 2018 |  | 2017
﻿Compensation charged against income before tax benefit | $ | 7,549 |  | 8,148
﻿Related income tax benefit recognized in income |  | 894 |  | 2,529
﻿

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- Definition Tabular disclosure of the amount of total share-based compensation cost, including the amounts attributable to each share-based compensation plan and any related tax benefits. + 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 (h)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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