Employee Stock and Incentive Plan (Summary Of Nonvested PSU Transactions) (Details) - $ / shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Number of Share Units	146,867	201,563	169,258
Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested stock units at beginning of period, Number of Share Units	443,410
Performance criteria adjustment, Number of Share Units	(82,921)
Forfeited, Number of Share Units	(9,767)
Share units issued, Number of Share Units	89,324
Nonvested stock units at end of period, Number of Share Units	261,398	443,410
Nonvested stock units at beginning of period, Weighted Average Fair Value	$ 27.20
Performance criteria adjustment, Weighted Average Fair Value	33.56
Forfeited, Weighted Average Fair Value	33.21
Share units issued, Weighted Average Fair Value	52.39
Nonvested stock units at end of period, Weighted Average Fair Value	$ 16.35	$ 27.20

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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=116856206&loc=d3e5070-113901

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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-Topic 718
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-Paragraph 2
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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).

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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.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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-Publisher FASB
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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.

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Number of shares issued under share-based payment arrangement.

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Share based compensation arrangement by share based payment award equity instruments other than options performance criteria adjustment

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