ASU 2018 - 12 Transition (Consolidated Balance Sheet Before After Transition Date) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Statements Adjusted [Abstract]
Deferred policy acquisition costs, net	$ 121,224	$ 128,463		$ 89,749	$ 131,187
Assets	19,058,758	18,100,734	$ 17,327,183	14,651,606	14,693,044
Policy benefits and losses, claims and loss expenses payable	849,113	880,202		909,701	1,040,951
Deferred Income Tax Liabilities, Net	1,447,125	1,329,489		1,199,280	1,182,123
Total liabilities	11,886,313	11,596,543		9,732,515	9,846,608
Accumulated other comprehensive loss	223,216	285,623		106,857	42,319
Retained earnings	7,600,090	7,003,148		5,025,568	5,017,451
Stockholders' Equity Attributable to Parent	7,172,445	6,504,191		4,919,091	4,846,436
Liabilities and Equity	$ 19,058,758	$ 18,100,734		$ 14,651,606	$ 14,693,044