Provision for Taxes (Significant Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Mar. 31, 2024
Deferred tax assets:
Net operating loss and credit carry forwards	$ 45,140	$ 36,978
Accrued expenses	120,725	108,512
Policy benefits and losses, claims and loss expenses payable, net	36,072	33,736
Unrealized losses	35,272	32,856
Operating leases, assets	9,849	11,521
Total deferred tax assets	259,839	232,572
Deferred tax liabilities:
Property, plant and equipment	1,728,789	1,655,074
Operating leases, liabilities	9,628	11,214
Deferred policy acquisition costs	11,342	10,709
Other		2,700
Total deferred tax liabilities	1,749,759	1,679,697
Net deferred tax liability	$ 1,489,920	$ 1,447,125

Amount of deferred tax assets attributable to taxable temporary differences from leasing arrangements.

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- Definition

This extended concept is a combination of two different concepts on the US-GAAP taxonomy: (1) DeferredTaxLiabilitiesUnrealizedGainsOnTradingSecurities: "Amount of deferred tax liability attributable to taxable temporary differences from unrealized gains on trading securities." (2) DeferredTaxLiabilitiesUnrealizedCurrencyTransactionGains: "Amount of deferred tax liability attributable to taxable temporary differences from unrealized gains on foreign currency transactions."

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- Definition

Amount of deferred tax liability attributable to taxable temporary differences.

+ References

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- Definition

Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences with jurisdictional netting.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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- Definition

Amount, before allocation of a valuation allowances, of deferred tax assets attributable to deductible tax credit carryforwards including, but not limited to, research, foreign, general business, alternative minimum tax, and other deductible tax credit carryforwards.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from accrued liabilities.

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- Definition

The tax effect as of the balance sheet date of the amount of the estimated future tax deductions arising from estimated policyholder reserves, which will be deductible from future taxable income when actual costs are incurred, and which can only be realized if sufficient tax-basis income is generated in future periods to enable the tax deduction to be taken.

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- Definition

The amount as of the balance sheet date of the estimated future tax effects attributable to policy acquisition costs being expensed for tax purposes but capitalized in conformity with generally accepted accounting principles, which will reverse in future periods when amortization of such capitalized costs cannot be deducted for tax purposes.

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- Definition

Amount of deferred tax liability attributable to taxable temporary differences from leasing arrangements.

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- Definition

Amount of deferred tax liability attributable to taxable temporary differences classified as other.

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- Definition

Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

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