Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Comprehensive income (loss) (pretax):
Net earnings	$ 1,475,497	$ 796,658	$ 378,124
Comprehensive income (loss) (tax effect):
Net earnings	(352,211)	(185,802)	63,924
Comprehensive income (loss) (net of tax):
Net earnings	1,123,286	610,856	442,048
Other comprehensive income (loss):
Foreign currency translation (pretax)	(2,828)	(5,694)	9,377
Foreign currency translation (tax effect)	0	0	0
Foreign currency translation (net of tax)	(2,828)	(5,694)	9,377
Unrealized gain (loss) on investments (pretax)	(78,452)	96,170	124,566
Unrealized gain (loss) on investments (tax effect)	15,826	(19,201)	(26,623)
Unrealized gain (loss) on investments (net of tax)	(62,626)	76,969	97,943
Change in fair value of cash flow hedges (pretax)	605	(569)	(8,352)
Change in fair value of cash flow hedges (tax effect)	(148)	140	2,051
Change in fair value of cash flow hedges (net of tax)	457	(429)	(6,301)
Amounts reclassified into earnings on hedging activities, (pre tax)	3,948	3,640	(3)
Amounts reclassified into earnings on hedging activities (tax effect)	(970)	(894)	1
Amounts reclassified into earnings on hedging,( net of tax)	2,978	2,746	(2)
Postretirement benefit obligation gain (loss) (pretax)	2,049	(1,838)	441
Postretirement benefit obligation gain (loss) (tax effect)	(503)	451	(108)
Postretirement benefit obligation gain (loss) (net of tax)	1,546	(1,387)	333
Total other comprehensive income (loss) (pretax)	(74,678)	91,709	126,029
Total other comprehensive income (loss) (tax effect)	14,205	(19,504)	(24,679)
Total other comprehensive income loss, net	(60,473)	72,205	101,350
Total comprehensive income	1,400,819	888,367	504,153
Total comprehensive income, tax	(338,006)	(205,306)	39,245
Total comprehensive income, net	$ 1,062,813	$ 683,061	$ 543,398