Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Comprehensive income (loss) (pretax):
Pretax earnings (loss)	$ 351,019	$ 205,354	$ 465,337	$ 380,068
Comprehensive income (loss) (tax effect):
Income tax expense	(84,654)	(49,028)	(111,246)	(91,320)
Comprehensive income (loss) (net of tax):
Net earnings	266,365	156,326	354,091	288,748
Other comprehensive income (loss):
Foreign currency translation (pretax)	290	629	(2,627)	3,611
Foreign currency translation (tax effect)	0	0	0	0
Foreign currency translation (net of tax)	290	629	(2,627)	3,611
Unrealized gain (loss) on investments (pretax)	115,186	52,651	56,224	104,478
Unrealized gain (loss) on investments (tax effect)	(24,347)	(11,346)	(10,884)	(22,385)
Unrealized gain (loss) on investments (net of tax)	90,839	41,305	45,340	82,093
Change in fair value of cash flow hedges (pretax)	46	(840)	(659)	(2,034)
Change in fair value of cash flow hedges (tax effect)	(11)	207	162	500
Change in fair value of cash flow hedges (net of tax)	35	(633)	(497)	(1,534)
Amounts reclassified into earnings on hedging activities (pre tax)	961	(366)	1,708	(425)
Amounts reclassified into earnings on hedging activities (tax effect)	(237)	89	(420)	104
Amounts reclassified into earnings on hedging activities (net of tax)	724	(277)	1,288	(321)
Total other comprehensive income (loss) (pretax)	116,483	52,074	54,646	105,630
Total other comprehensive income (loss) (tax effect)	(24,595)	(11,050)	(11,142)	(21,781)
Total other comprehensive income (loss) (net of tax)	91,888	41,024	43,504	83,849
Total comprehensive income (loss) (pretax)	467,502	257,428	519,983	485,698
Total comprehensive income (loss) (tax effect)	(109,249)	(60,078)	(122,388)	(113,101)
Total comprehensive income (loss) (net of tax)	$ 358,253	$ 197,350	$ 397,595	$ 372,597