Accounting Pronouncements (Consolidated Balance Sheet Before After Transition Date (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Mar. 31, 2022	Mar. 31, 2021
Statements Adjusted [Abstract]
Deferred policy acquisition costs, net	$ 123,596	$ 128,463
Assets	18,614,034	18,100,734	$ 17,793,811
Policy benefits and losses, claims and loss expenses payable	878,436	880,202
Deferred income taxes, net	1,371,859	1,329,489
Total liabilities	11,836,277	11,596,543
Accumulated other comprehensive loss	(261,836)	(285,623)
Retained earnings	7,252,927	7,003,148
Stockholders' Equity Attributable to Parent	6,777,757	6,504,191
Liabilities and Equity	$ 18,614,034	$ 18,100,734
Before Transition Date [Member]
Statements Adjusted [Abstract]
Deferred policy acquisition costs, net					$ 89,749
Assets					14,651,606
Policy benefits and losses, claims and loss expenses payable					909,701
Deferred income taxes, net					1,199,280
Total liabilities					9,732,515
Accumulated other comprehensive loss					106,857
Retained earnings					5,025,568
Stockholders' Equity Attributable to Parent					4,919,091
Liabilities and Equity					$ 14,651,606
After Transition Date [Member]
Statements Adjusted [Abstract]
Deferred policy acquisition costs, net				$ 131,187
Assets				14,693,044
Policy benefits and losses, claims and loss expenses payable				1,040,951
Deferred income taxes, net				1,182,123
Total liabilities				9,846,608
Accumulated other comprehensive loss				42,319
Retained earnings				5,017,451
Stockholders' Equity Attributable to Parent				4,846,436
Liabilities and Equity				$ 14,693,044