Provision for Taxes (Table Text Block)	12 Months Ended
Mar. 31, 2022
Table Text Block [Abstract]
Provision For Taxes	Years Ended March 31, 2022 2021 2020 (In thousands) Pretax earnings: U.S. $ 1,431,155 $ 773,030 $ 372,687 Non-U.S. 44,342 23,628 5,437 Total pretax earnings $ 1,475,497 $ 796,658 $ 378,124 Current provision (benefit) Federal $ 189,488 $ 100,521 $ (373,817) State 55,518 16,572 (9,600) Non-U.S. 6,893 3,404 949 251,899 120,497 (382,468) Deferred provision (benefit) Federal 90,852 53,957 307,846 State 6,355 9,795 9,728 Non-U.S. 3,105 1,553 970 100,312 65,305 318,544 Provision for income tax expense (benefit) $ 352,211 $ 185,802 $ (63,924) Income taxes paid (net of income tax refunds received)$( 4,548 )$ 29,044 $ 6,859
Schedule of Effective Income Tax Rate Reconciliation	Years Ended March 31, 2022 2021 2020 (In percentages) Statutory federal income tax rate 21.00 % 21.00 % 21.00 % Increase (reduction) in rate resulting from: NOL tax rate benefit – % – % (38.62) % State taxes, net of federal benefit 3.24 % 2.53 % 0.02 % Foreign rate differential 0.05 % – % 0.21 % Federal tax credits (0.19) % (0.99) % (0.53) % Transition tax – % – % – % Tax-exempt income (0.03) % (0.08) % (0.17) % Dividend received deduction – % (0.01) % (0.01) % Other (0.20) % 0.87 % 1.19 % Actual tax expense (benefit) of operations 23.87 % 23.32 %( 16.91 )%
Components of Deferred Tax Assets and Liabilities	March 31, 2022 2021 Deferred tax assets: (In thousands) Net operating loss and credit carry forwards $ 36,367 $ 30,432 Accrued expenses 114,152 109,740 Policy benefit and losses, claims and loss expenses payable, net 30,572 26,799 Operating leases 15,540 19,370 Total deferred tax assets $ 196,631 $ 186,341 Deferred tax liabilities: Property, plant and equipment $ 1,395,216 $ 1,280,703 Operating leases 15,540 19,370 Deferred policy acquisition costs 12,962 13,696 Unrealized gains 36,299 48,667 Other 1,972 2,394 Total deferred tax liabilities 1,461,989 1,364,830 Net deferred tax liability$ 1,265,358 $ 1,178,489
Reconciliation of Total Amounts of Unrecognized Tax Benefits	Unrecognized Tax Benefits March 31, 2022 2021 (In thousands) Unrecognized tax benefits beginning balance $ 31,069 $ 29,632 Revaluation based on change in after tax benefit – – Additions based on tax positions related to the current year 8,257 1,479 Reductions for tax positions of prior years – (42) Additions for tax provisions of prior years 9,525 – Unrecognized tax benefits ending balance$ 48,851 $ 31,069

Tabular disclosure of the components of income tax expense attributable to continuing operations for each year presented including, but not limited to: current tax expense (benefit), deferred tax expense (benefit), investment tax credits, government grants, the benefits of operating loss carryforwards, tax expense that results from allocating certain tax benefits either directly to contributed capital or to reduce goodwill or other noncurrent intangible assets of an acquired entity, adjustments of a deferred tax liability or asset for enacted changes in tax laws or rates or a change in the tax status of the entity, and adjustments of the beginning-of-the-year balances of a valuation allowance because of a change in circumstances that causes a change in judgment about the realizability of the related deferred tax asset in future years.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32639-109319

+ Details

Name:	us-gaap_ScheduleOfComponentsOfIncomeTaxExpenseBenefitTableTextBlock
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration

- Definition

Tabular disclosure of the components of net deferred tax asset or liability recognized in an entity's statement of financial position, including the following: the total of all deferred tax liabilities, the total of all deferred tax assets, the total valuation allowance recognized for deferred tax assets.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32537-109319

+ Details

Name:	us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration

- Definition

Tabular disclosure of the reconciliation using percentage or dollar amounts of the reported amount of income tax expense attributable to continuing operations for the year to the amount of income tax expense that would result from applying domestic federal statutory tax rates to pretax income from continuing operations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32687-109319

+ Details

Name:	us-gaap_ScheduleOfEffectiveIncomeTaxRateReconciliationTableTextBlock
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration

- Definition

Tabular disclosure for tax positions taken in the tax returns filed or to be filed for which it is more likely than not that the tax position will not be sustained upon examination by taxing authorities and other income tax contingencies. Includes, but is not limited to, interest and penalties, reconciliation of unrecognized tax benefits, unrecognized tax benefits that would affect the effective tax rate, tax years that remain subject to examination by tax jurisdictions, and information about positions for which it is reasonably possible that amounts unrecognized will significantly change within 12 months.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-URI http://asc.fasb.org/extlink&oid=121826272&loc=SL6600010-109319

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32718-109319

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 19
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32840-109319

+ Details

Name:	us-gaap_SummaryOfIncomeTaxContingenciesTextBlock
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_TableTextBlock
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration