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Stock-Based Compensation (Stock Appreciation Rights Award Activity) (Details) - $ / shares | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
SARs, Weighted Average Exercise Price [Roll Forward] |  |  |
Stock-Settled SARs, Outstanding | 21,980 |  |
Cash-Settled SARs, Outstanding | 29,388 |  |
Stock Appreciation Rights (SARs) [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Awards, expiration period | 10 years |  |
SARs Activity [Roll Forward] |  |  |
Outstanding, Beginning | 116,087 | 232,930 | 297,714
Granted | 2,792 | 3,368 | 12,356
Exercised | (67,511) | (114,976) | (77,140)
Outstanding, Ending | 51,368 | 116,087 | 232,930
Exercisable | 39,769 | 71,701 | 112,295
SARs, Weighted Average Exercise Price [Roll Forward] |  |  |
Oustanding, Beginning (in usd per share) | $ 31.13 | $ 27.79 | $ 25.20
Granted (in usd per share) | 83.47 | 68.40 | 57.25
Exercised (in usd per share) | 27.65 | 24.95 | 22.52
Oustanding, Ending (in usd per share) | 38.55 | 31.13 | 27.79
Exercisable (in usd per share) | 30.77 | 26.65 | 24.60
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures in Period, Weighted Average Exercise Price | $ 0.00 | $ 42.28 | $ 0.00
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures | 0 | (5,235) | 0

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- Definition Number of non-option equity instruments exercised by participants. + 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)(iv)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Number of shares under non-option equity instrument agreements that were cancelled as a result of occurrence of a terminating event. + 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)(iv)(3) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Net number of non-option equity instruments granted to participants. + 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)(iv)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Number of equity instruments other than options outstanding, including both vested and non-vested instruments. + 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) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(ii) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + 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 (a)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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