Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022
Comprehensive income (loss) (pretax):
Pretax earnings (loss)	$ 129,773	$ 260,616	$ 826,516	$ 1,167,505
Comprehensive income (loss) (tax effect):
Income tax expense	(30,549)	(61,764)	(196,946)	(280,442)
Comprehensive income (loss) (net of tax):
Net Income (Loss)	99,224	198,852	629,570	887,063
Other comprehensive income (loss):
Foreign currency translation (pretax)	5,268	(215)	2,888	(757)
Foreign currency translation (tax effect)	0	0	0	0
Foreign currency translation (net of tax)	5,268	215	2,888	757
Unrealized gain (loss) on investments (pretax)	41,618	(75,876)	32,942	(386,758)
Unrealized gain (loss) on investments (tax effect)	(8,833)	16,082	(7,204)	82,138
Unrealized gain (loss) on investments (net of tax)	32,785	59,794	25,738	304,620
Change in fair value cash flow hedges (pretax)	5,769	153	3,742	8,659
Change in fair value of cash flow hedges (tax effect)	(1,417)	(38)	(919)	(2,127)
Change in fair value of cash flow hedges, (net of tax)	4,352	115	2,823	6,532
Amounts reclassified into earnings on hedging activities (pre tax)	1,471	(456)	3,966	134
Amounts reclassified into earnings on hedging activities (tax effect)	(362)	111	(974)	(33)
Amounts reclassified into earnings on hedging activities (net of tax)	1,109	345	2,992	101
Total other comprehensive income (loss) (pretax)	43,590	(76,394)	30,278	(378,722)
Total other comprehensive income (loss) (tax effect)	(10,612)	16,155	(7,259)	79,978
Total other comprehensive income (loss) (net of tax)	32,978	60,239	23,019	298,744
Total comprehensive income (loss) (pretax)	86,183	184,222	796,238	788,783
Total comprehensive income (loss) (tax effect)	(19,937)	(45,609)	(189,687)	(200,464)
Total comprehensive income (loss) (net of tax)	$ 66,246	$ 138,613	$ 606,551	$ 588,319