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Stock-Based Compensation - Stock Appreciation Rights Award Activity (Details) - Stock Appreciation Rights (SARs) - $ / shares | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Awards, expiration period | 10 years |  |
SARs Activity [Roll Forward] |  |  |
Outstanding, beginning (in shares) | 35,993 | 39,819 | 51,368
Granted (in shares) | 3,272 | 3,364 | 3,480
Exercised (in shares) | (11,261) | (6,790) | (14,629)
Forfeited (in shares) | (325) | (400) | (400)
Outstanding, ending (in shares) | 27,679 | 35,993 | 39,819
Exercisable (in shares) | 27,182 | 27,781 | 30,285
SARs, Weighted Average Exercise Price [Roll Forward] |  |  |
Outstanding, beginning (in dollars per share) | $ 52.36 | $ 46.48 | $ 38.55
Granted (in dollars per share) | 190.97 | 102.51 | 89.64
Exercised (in dollars per share) | 35.37 | 42.08 | 28.45
Forfeited (in dollars per share) | 71.43 | 63.43 | 63.43
Outstanding, ending (in dollars per share) | 75.43 | 52.36 | 46.48
Exercisable (in dollars per share) | $ 40.23 | $ 40.73 | $ 36.91

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- Definition Number of non-option equity instruments exercised by participants. + 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)(iv)(2) -URI http://asc.fasb.org/extlink&oid=120381028&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://fasb.org/us-gaap/role/ref/legacyRef -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=120381028&loc=d3e5070-113901 + Details
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- Definition Net number of non-option equity instruments granted to participants. + 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)(iv)(1) -URI http://asc.fasb.org/extlink&oid=120381028&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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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