Accumulated Other Comprehensive Income Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31	$ 46,384
Foreign currency translation	(782)	$ (2,828)	$ (5,694)
Unrealized net loss on investments	(319,190)	(62,626)	76,969
Amounts reclassified into earnings on hedging activities	(582)	2,978	2,746
Change in post retirement benefit obligations	2,091	1,546	(1,387)
Other comprehensive income (loss)	(313,430)	(60,473)	72,205
Ending balance as of March 31	(267,046)	46,384
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31	(55,757)	(52,929)	(47,235)
Foreign currency translation	(782)	(2,828)	(5,694)
Unrealized net loss on investments	0	0	0
Change in fair value of cash flow hedges	0	0	0
Amounts reclassified into earnings on hedging activities	0	0	0
Change in post retirement benefit obligations	0	0	0
Other comprehensive income (loss)	(782)	(2,828)	(5,694)
Ending balance as of March 31	(56,539)	(55,757)	(52,929)
Unrealized Gain (Loss) on Investments
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31	105,027	167,653	90,684
Foreign currency translation	0	0	0
Unrealized net loss on investments	(319,190)	(62,626)	76,969
Change in fair value of cash flow hedges	0	0	0
Amounts reclassified into earnings on hedging activities	0	0	0
Change in post retirement benefit obligations	0	0	0
Other comprehensive income (loss)	(319,190)	(62,626)	76,969
Ending balance as of March 31	(214,163)	105,027	167,653
Fair Market Value of Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31	(444)	(3,879)	(6,196)
Foreign currency translation	0	0	0
Unrealized net loss on investments	0	0	0
Change in fair value of cash flow hedges	5,033	457	(429)
Amounts reclassified into earnings on hedging activities	(582)	2,978	2,746
Change in post retirement benefit obligations	0	0	0
Other comprehensive income (loss)	4,451	3,435	2,317
Ending balance as of March 31	4,007	(444)	(3,879)
Postretirement Benefit Obligation Gain (Loss)
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31	(2,442)	(3,988)	(2,601)
Foreign currency translation	0	0	0
Unrealized net loss on investments	0	0	0
Change in fair value of cash flow hedges	0	0	0
Amounts reclassified into earnings on hedging activities	0	0	0
Change in post retirement benefit obligations	2,091	1,546	(1,387)
Other comprehensive income (loss)	2,091	1,546	(1,387)
Ending balance as of March 31	(351)	(2,442)	(3,988)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Beginning balance as of March 31	46,384	106,857	34,652
Foreign currency translation	(782)	(2,828)	(5,694)
Unrealized net loss on investments	(319,190)	(62,626)	76,969
Change in fair value of cash flow hedges	5,033	457	(429)
Amounts reclassified into earnings on hedging activities	(582)	2,978	2,746
Change in post retirement benefit obligations	2,091	1,546	(1,387)
Other comprehensive income (loss)	(313,430)	(60,473)	72,205
Ending balance as of March 31	$ (267,046)	$ 46,384	$ 106,857