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Share-Based Compensation, Stock Equivalent Unit Plan (Details) - $ / shares | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Equity Instruments Other than Options Activity [Roll Forward] |  |  |
Balance at January 1 (in shares) | 995,000 |  |
Granted (in shares) | 500,000 | 503,000 | 522,000
Dividend equivalents (in shares) | 45,000 |  |
Balance at December 31 (in shares) | 939,000 | 995,000 |
Equity Instruments Other than Options, Weighted Average Grant Date Fair Value [Abstract] |  |  |
Balance at January 1, weighted average grant date fair value (in dollars per share) | $ 38.48 |  |
Granted, weighted average grant date fair value (in dollars per share) | 47.60 | $ 41.02 | $ 36.00
Dividend equivalents, weighted average grant date fair value (in dollars per share) | 40.74 |  |
Balance at December 31, weighted average grant date fair value (in dollars per share) | $ 44.30 | $ 38.48 |
Stock Equivalent Units [Member] |  |  |
Equity Instruments Other than Options Activity [Roll Forward] |  |  |
Balance at January 1 (in shares) | 753,000 |  |
Granted (in shares) | 36,000 | 51,000 | 49,000
Units distributed (in shares) | (123,000) |  |
Dividend equivalents (in shares) | 22,000 |  |
Balance at December 31 (in shares) | 688,000 | 753,000 |
Equity Instruments Other than Options, Weighted Average Grant Date Fair Value [Abstract] |  |  |
Balance at January 1, weighted average grant date fair value (in dollars per share) | $ 29.83 |  |
Granted, weighted average grant date fair value (in dollars per share) | 45.44 | $ 46.05 | $ 40.68
Units distributed, weighted average grant date fair value (in dollars per share) | 31.21 |  |
Dividend equivalents, weighted average grant date fair value (in dollars per share) | 46.40 |  |
Balance at December 31, weighted average grant date fair value (in dollars per share) | $ 30.93 | $ 29.83 |
Equity Instruments Other than Options, Additional Disclosures [Abstract] |  |  |
Number of shares of common stock into which the share-based compensation can be converted (in shares) | 1 |  |

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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + 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)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + 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)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + 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)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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- Definition The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units. + 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)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The number of units under a share-based award plan other than a stock option plan that do not need to vest and are readily available, regardless of in stock equivalents or in cash, during the period in accordance with the terms of the arrangement. + References No definition available. + Details
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