Provision for Taxes (Significant components of deferred tax assets and liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Mar. 31, 2019
Deferred tax assets:
Net operating loss and credit carry forwards	$ 25,973	$ 90,061
Accrued expenses	105,171	105,727
Policy benefits and losses, claims and loss expenses payable, net	20,189	16,515
Operating leases, assets	22,353	0
Total deferred tax assets	173,686	212,303
Deferred tax liabilities:
Property, plant and equipment	1,198,198	940,433
Operating leases, liabilities	22,353	0
Deferred policy acquisition costs	12,795	14,191
Unrealized gains	29,873	4,223
Other	4,010	4,426
Total deferred tax liabilities	1,267,229	963,273
Net deferred tax liability	$ 1,093,543	$ 750,970