Provision for Taxes (Significant components of deferred tax assets and liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Mar. 31, 2015
Deferred tax assets:
Net operating loss and credit carry forwards	$ 1,462	$ 1,228
Accrued expenses	185,088	171,761
Policy benefits and losses, claims and loss expenses payable, net	$ 21,911	$ 19,560
Unrealized losses
Total deferred tax assets	$ 208,461	$ 192,549
Deferred tax liabilities:
Property, plant and equipment	831,914	680,501
Deferred policy acquisition costs	20,557	18,369
Unrealized gains	9,593	20,216
Other	9	262
Total deferred tax liabilities	862,073	719,348
Net deferred tax liability	$ 653,612	$ 526,799