Executive Stock Plans And Stock-Based Compensation (Summary Of RSU, Restricted Stock, And PSA Activity) (Details) - $ / shares shares in Thousands	12 Months Ended
Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2019
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Shares	100,105	93,564	103,829
Vested, Shares	(67,239)	(86,488)	(97,297)
Forfeited, Shares	0	0	0
Unvested at end of year, Shares	382,410	349,544	342,468	335,936
Granted, Weighted- Average Grant Date Fair Value	$ 60.89	$ 56.18	$ 46.27
Vested, Weighted- Average Grant Date Fair Value	62.39	54.33	54.11
Forfeited, Weighted- Average Grant Date Fair Value	0	0	0
Unvested at end of year, Weighted- Average Grant Date Fair Value	$ 56.03	$ 55.86	$ 55.44	$ 57.89
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Shares	0	0	0
Vested, Shares	0	0	(9,650)
Forfeited, Shares	0	0	0
Unvested at end of year, Shares	11,600	11,600	11,600	21,250
Granted, Weighted- Average Grant Date Fair Value	$ 0	$ 0	$ 0
Vested, Weighted- Average Grant Date Fair Value	0	0	41.24
Forfeited, Weighted- Average Grant Date Fair Value	0	0	0
Unvested at end of year, Weighted- Average Grant Date Fair Value	$ 41.86	$ 41.86	$ 41.86	$ 41.58
Performance Share Awards Psas [Member
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Shares	48,315	48,650	65,135
Vested, Shares	(37,040)	(50,242)	(40,410)
Forfeited, Shares	(9,260)	(1,555)	(3,778)
Unvested at end of year, Shares	160,015	158,000	161,147	140,200
Granted, Weighted- Average Grant Date Fair Value	$ 54.46	$ 47.95	$ 34.33
Vested, Weighted- Average Grant Date Fair Value	50.16	57.12	60.37
Forfeited, Weighted- Average Grant Date Fair Value	50.16	57.12	57.83
Unvested at end of year, Weighted- Average Grant Date Fair Value	$ 44.55	$ 43.16	$ 46.20	$ 55.73

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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- 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/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(ii)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(ii)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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- Definition

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

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- Definition

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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- 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.

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No definition available.

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