Accumulated Other Comprehensive Loss (Summary of Accumulated Other Comprehensive Income (Loss) Components, Net of Tax) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Balance as of March 31, 2023			$ 223,216
Foreign currency translation	$ 421	$ 2,849	217	$ 2,380
Unrealized net gain on investments	4,032	13,297	9,445	7,047
Change in fair value of cash flow hedges	1,696	3,333	209	7,175
Amount reclassified from AOCI	7,103	1,015	8,178	1,883
Other comprehensive income (loss)	9,018	13,828	17,615	9,959
Balance as of June 30, 2024	240,831		240,831
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Balance as of March 31, 2023			53,707	56,539
Foreign currency translation			217	2,380
Other comprehensive income (loss)			217	2,380
Balance as of June 30, 2024	53,490	58,919	53,490	58,919
Unrealized Net Gain on Investments [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Balance as of March 31, 2023			176,883	232,740
Unrealized net gain on investments			9,445	7,047
Other comprehensive income (loss)			9,445	7,047
Balance as of June 30, 2024	186,328	225,693	186,328	225,693
Fair Market Value of Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Balance as of March 31, 2023			6,330	4,007
Change in fair value of cash flow hedges			209	7,175
Amount reclassified from AOCI			8,178	1,883
Other comprehensive income (loss)			8,387	5,292
Balance as of June 30, 2024	2,057	9,299	2,057	9,299
Postretirement Benefit Obligation Gain [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Balance as of March 31, 2023			1,044	351
Balance as of June 30, 2024	1,044	351	1,044	351
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Balance as of March 31, 2023			223,216	285,623
Foreign currency translation	421	2,849	217	2,380
Unrealized net gain on investments	4,032	13,297	9,445	7,047
Change in fair value of cash flow hedges	1,696	3,333	209	7,175
Amount reclassified from AOCI	7,103	1,015	8,178	1,883
Other comprehensive income (loss)			17,615	9,959
Balance as of June 30, 2024	$ 240,831	$ 275,664	$ 240,831	$ 275,664