Stock-Based Compensation (Summary Of Nonvested Shares) (Details) - $ / shares	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Performance Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Requisite Service Period	5 years
Fully Vested Undistributed Retirement-eligible units (in shares)	619,783	712,572
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share Units, Nonvested at beginning of year (in shares)	895,489
Share Units, Granted (in shares)	316,875
Share Units, Unearned or forfeited (in shares)	(65,106)
Undistributed Vested Units (in shares)	(288,404)
Share Units, Vested and distributed (in shares)	(176,043)
Share Units, Nonvested at end of year (in shares)	682,811	895,489
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted-average Fair Value per Unit, Nonvested at beginning of year (in dollars per share)	$ 52.28
Weighted-average Fair Value per Unit, Granted (in dollars per share)	62.88	$ 59.16	$ 44.13
Weighted-average Fair Value per Unit, Unearned or forfeited (in dollars per share)	51.11
Weighted-average Fair Value per Unit, Vested and undistributed (in dollars per share)	53.63
Weighted-average Fair Value per Unit, Vested and distributed (in dollars per share0	52.88
Weighted-average Fair Value per Unit, Nonvested at end of year (in dollars per share)	$ 56.58	$ 52.28
Performance period	3 years
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fully Vested Undistributed Retirement-eligible units (in shares)	26,557
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share Units, Nonvested at beginning of year (in shares)	0
Share Units, Granted (in shares)	187,273
Share Units, Unearned or forfeited (in shares)	(5,463)
Undistributed Vested Units (in shares)	(26,557)
Share Units, Vested and distributed (in shares)	0
Share Units, Nonvested at end of year (in shares)	155,253	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted-average Fair Value per Unit, Nonvested at beginning of year (in dollars per share)	$ 0.00
Weighted-average Fair Value per Unit, Granted (in dollars per share)	57.66
Weighted-average Fair Value per Unit, Unearned or forfeited (in dollars per share)	58.99
Weighted-average Fair Value per Unit, Vested and undistributed (in dollars per share)	59.02
Weighted-average Fair Value per Unit, Vested and distributed (in dollars per share0	0.00
Weighted-average Fair Value per Unit, Nonvested at end of year (in dollars per share)	$ 57.38	$ 0.00

Share-based Compensation Arrangement by Share-based Payment Award, Performance Period

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Fully Vested Undistributed to Retirement-eligible employees.

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

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan that vested during the reporting period but were undistributed.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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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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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 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).

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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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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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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.

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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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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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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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