Accumulated Other Comprehensive Income (Loss) (Summary of Accumulated Other Comprehensive Income (Loss) Components, Net of Tax) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31	$ 285,623		$ 106,857
Foreign currency translation	2,832	$ 782	2,828
Unrealized net loss on investments	55,857	289,477	46,378
Change in fair value of cash flow hedges	6,410	5,033	457
Amounts reclassified into earnings on hedging activities	4,087	582	2,978
Change in post retirement benefit obligations	1,395	2,091	1,546
Other comprehensive income (loss)	62,407	283,717	44,225
Ending balance as of March 31	223,216	285,623
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31	56,539	55,757	52,929
Foreign currency translation	2,832	782	2,828
Other comprehensive income (loss)	2,832	782	2,828
Ending balance as of March 31	53,707	56,539	55,757
Unrealized Net Gains (Losses) on Investments [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31	232,740	56,737	167,653
Unrealized net loss on investments	55,857	289,477	46,378
Other comprehensive income (loss)	55,857	289,477	46,378
Ending balance as of March 31	176,883	232,740	56,737
Fair Market Value of Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31	4,007	444	3,879
Change in fair value of cash flow hedges	6,410	5,033	457
Amounts reclassified into earnings on hedging activities	4,087	582	2,978
Other comprehensive income (loss)	2,323	4,451	3,435
Ending balance as of March 31	6,330	4,007	444
Postretirement Benefit Obligation Net Loss [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31	351	2,442	3,988
Change in post retirement benefit obligations	1,395	2,091	1,546
Other comprehensive income (loss)	1,395	2,091	1,546
Ending balance as of March 31	1,044	351	2,442
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31	285,623	1,906	106,857
Foreign currency translation	2,832	782	2,828
Unrealized net loss on investments	55,857	289,477	46,378
Change in fair value of cash flow hedges	6,410	5,033	457
Amounts reclassified into earnings on hedging activities	4,087	582	2,978
Change in post retirement benefit obligations	1,395	2,091	1,546
Other comprehensive income (loss)	62,407	283,717	44,225
Ending balance as of March 31	$ 223,216	$ 285,623	1,906
Cumulative Effect, Period of Adoption, Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31			64,538
Cumulative Effect, Period of Adoption, Adjustment [Member] | Unrealized Net Gains (Losses) on Investments [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31			64,538
Cumulative Effect, Period of Adoption, Adjustment [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31			17,156
Cumulative Effect, Period of Adoption, Adjusted Balance [Member] | Unrealized Net Gains (Losses) on Investments [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31			103,115
Cumulative Effect, Period of Adoption, Adjusted Balance [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31			$ 42,319