Benefit Plans (Summary Of Performance Shares and Performance Units Activity) (Details) - $ / shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Performance Shares Equity Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	0
Nonvested, January 1, weighted average grant date fair value (in dollars per share)	$ 0
Granted (in shares/awards)	91,816
Granted, weighted average grant date fair value (in dollars per share)	$ 47.23
Forfeited (in shares/awards)	(17,623)
Forfeited, weighted average grant date fair value (in dollars per share)	$ 46.35
Nonvested, December 31 (in shares/awards)	74,193	0
Nonvested, December 31, weighted average grant date fair value (in dollars per share)	$ 47.44	$ 0
Performance Shares Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	203,188	223,511	257,599
Granted (in shares/awards)	0	74,163	65,350
Vested (in shares/awards)	(66,322)	(90,806)	(99,438)
Forfeited (in shares/awards)	(4,994)	(3,680)	0
Nonvested, December 31 (in shares/awards)	131,872	203,188	223,511
Performance Units Liability Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested, January 1 (in shares/awards)	57,761	71,737	93,320
Granted (in shares/awards)	0	19,840	21,558
Vested (in shares/awards)	(20,131)	(31,910)	(37,395)
Forfeited (in shares/awards)	(3,056)	(1,906)	(5,746)
Nonvested, December 31 (in shares/awards)	34,574	57,761	71,737

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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- Definition

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.

+ 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
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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).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 2
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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
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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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-Publisher FASB
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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.

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

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