Provision for Taxes (Significant components of deferred tax assets and liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Mar. 31, 2022
Deferred tax assets:
Net operating loss and credit carry forwards	$ 33,778	$ 36,394
Accrued expenses	112,971	103,723
Policy benefits and losses, claims and loss expenses payable, net	31,436	30,572
Unrealized losses	48,179	0
Operating leases, assets	12,058	15,540
Total deferred tax assets	238,422	186,229
Deferred tax liabilities:
Property, plant and equipment	1,545,628	1,405,604
Operating leases, liabilities	12,175	15,540
Deferred policy acquisition costs	12,038	12,962
Unrealized gains	0	36,299
Other	3,008	1,973
Total deferred tax liabilities	1,572,849	1,472,378
Net deferred tax liability	$ 1,334,427	$ 1,286,149