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Benefit Plans (Fair Values Of Nonvested Performance Shares And Performance Units) (Details) - $ / shares | 3 Months Ended |
--- | --- | ---
Mar. 31, 2018 | Dec. 31, 2017
Performance Shares [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Nonvested awards at target (in shares/awards) | 206,868 | 223,511
Performance Units [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Nonvested awards at target (in shares/awards) | 59,667 | 71,737
2018 Grant [Member] | Performance Shares [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Nonvested awards at target (in shares/awards) | 74,163 |
Estimated payout percentage based on performance criteria | 100.00% |
Fair values of each nonvested award (in dollars per share) | $ 40.86 |
2018 Grant [Member] | Performance Units [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Nonvested awards at target (in shares/awards) | 19,840 |
Estimated payout percentage based on performance criteria | 100.00% |
Fair values of each nonvested award (in dollars per share) | $ 40.86 |
2017 Grant [Member] | Performance Shares [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Nonvested awards at target (in shares/awards) | 65,350 |
Estimated payout percentage based on performance criteria | 115.00% |
Fair values of each nonvested award (in dollars per share) | $ 46.99 |
2017 Grant [Member] | Performance Units [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Nonvested awards at target (in shares/awards) | 18,600 |
Estimated payout percentage based on performance criteria | 115.00% |
Fair values of each nonvested award (in dollars per share) | $ 46.99 |
2016 Grant [Member] | Performance Shares [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Nonvested awards at target (in shares/awards) | 67,355 |
Estimated payout percentage based on performance criteria | 160.00% |
Fair values of each nonvested award (in dollars per share) | $ 65.38 |
2016 Grant [Member] | Performance Units [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Nonvested awards at target (in shares/awards) | 21,227 |
Estimated payout percentage based on performance criteria | 160.00% |
Fair values of each nonvested award (in dollars per share) | $ 65.38 |

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + 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://www.xbrl.org/2003/role/presentationRef -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=96867065&loc=d3e5070-113901 + Details
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