Executive Stock Plans And Stock-Based Compensation (Summary Of RSU, Restricted Stock, And PSA Activity) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Shares	94,539	70,092	87,780
Vested, Shares	(123,322)	(69,046)	(86,925)
Forfeited, Shares	0	0	0
Unvested at end of year, Shares	264,397	293,180	292,134	291,279
Granted, Weighted- Average Grant Date Fair Value	$ 51.86	$ 57.79	$ 44.06
Vested, Weighted- Average Grant Date Fair Value	$ 42.02	$ 44.89	$ 52.42
Forfeited, Weighted- Average Grant Date Fair Value	$ 0.00	$ 0.00	$ 0.00
Unvested at end of year, Weighted- Average Grant Date Fair Value	$ 48.10	$ 44.33	$ 41.23	$ 43.72
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Shares	0	0	0
Vested, Shares	0	(11,750)	(7,550)
Forfeited, Shares	0	0	0
Unvested at end of year, Shares	48,100	48,100	59,850	67,400
Granted, Weighted- Average Grant Date Fair Value	$ 0.00	$ 0.00	$ 0.00
Vested, Weighted- Average Grant Date Fair Value	$ 0.00	$ 39.02	$ 43.74
Forfeited, Weighted- Average Grant Date Fair Value	$ 0.00	$ 0.00	$ 0.00
Unvested at end of year, Weighted- Average Grant Date Fair Value	$ 42.33	$ 42.33	$ 41.68	$ 41.91
Performance Share Awards Psas [Member
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Shares	57,580	52,400	92,425
Vested, Shares	(50,092)	(32,464)	(94,725)
Forfeited, Shares	(3,400)	(5,566)	(5,149)
Unvested at end of year, Shares	153,475	149,387	135,017	142,466
Granted, Weighted- Average Grant Date Fair Value	$ 46.41	$ 53.56	$ 35.25
Vested, Weighted- Average Grant Date Fair Value	$ 31.95	$ 33.95	$ 29.67
Forfeited, Weighted- Average Grant Date Fair Value	$ 53.56	$ 37.45	$ 36.15
Unvested at end of year, Weighted- Average Grant Date Fair Value	$ 45.58	$ 41.76	$ 35.12	$ 31.45

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

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)(1)(iv)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&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://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

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

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)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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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://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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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=6415400&loc=d3e5070-113901

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- Definition

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.

+ 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=6415400&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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

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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.

+ 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)(iii)(2)

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