Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Comprehensive income (loss) (pretax):
Pretax earnings (loss)	$ 205,354	$ 215,660	$ 380,068	$ 384,857
Comprehensive income (loss) (net of tax):
Net earnings	156,326	163,542	288,748	291,391
Other comprehensive income (loss):
Foreign currency translation (pretax)	629	1,113	3,611	(980)
Foreign currency translation (tax effect)
Foreign currency translation (net of tax)	629	1,113	3,611	(980)
Unrealized gain (loss) on investments (pretax)	52,651	(22,280)	104,478	(72,498)
Unrealized gain (loss) on investments (tax effect)	(11,346)	4,679	(22,385)	15,225
Unrealized gain (loss) on investments (net of tax)	41,305	(17,601)	82,093
Change in fair value of cash flow hedges (pretax)	(840)	477	(2,034)
Change in fair value of cash flow hedges (tax effect)	207	(117)	500	(418)
Change in fair value of cash flow hedges (net of tax)	(633)	360		1,283
Amounts reclassified into earnings on hedging activities, (pre tax)	(366)	(191)	(425)	(855)
Amounts reclassified into earnings on hedging activities (tax effect)	89	47	104	210
Amounts reclassified into earnings on hedging activities, net			(321)	(645)
Total comprehensive income (loss) (pretax)	257,428	194,779	485,698	312,225
Total comprehensive income (loss) (tax effect)	(60,078)	(47,509)	(113,101)	(78,449)
Total comprehensive income (loss) (net of tax)	$ 197,350	$ 147,270	$ 372,597	$ 233,776