Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Comprehensive income (loss) (pretax):
Pretax earnings (loss)	$ 241,571	$ 40,329	$ 706,908	$ 420,397
Comprehensive income (loss) (tax effect):
Income tax expense	(58,586)	(9,397)	(169,832)	(100,717)
Comprehensive income (loss) (net of tax):
Net earnings	182,985	30,932	537,076	319,680
Other comprehensive income (loss):
Foreign currency translation (pretax)	(2,566)	(692)	(5,193)	2,919
Foreign currency translation (tax effect)	0	0	0	0
Foreign currency translation (net of tax)	(2,566)	(692)	(5,193)	2,919
Unrealized gain (loss) on investments (pretax)	12,074	28,568	68,298	133,046
Unrealized gain (loss) on investments (tax effect)	(2,514)	(6,190)	(13,398)	(28,575)
Unrealized gain (loss) on investments (net of tax)	9,560	22,378	54,900	104,471
Change in fair value of cash flow hedges (pretax)	35	479	(624)	(1,555)
Change in fair value of cash flow hedges (tax effect)	(9)	(118)	153	382
Change in fair value of cash flow hedges (net of tax)	26	361	(471)	(1,173)
Amounts reclassified into earnings on hedging activities, (pre tax)	972	422	2,680	(3)
Amounts reclassified into earnings on hedging activities (tax effect)	(238)	(103)	(658)	1
Amounts reclassified into earnings on hedging activities (net of tax)	734	319	2,022	(2)
Total other comprehensive income (loss) (pretax)	10,515	28,777	65,161	134,407
Total other comprehensive income (loss) (tax effect)	(2,761)	(6,411)	(13,903)	(28,192)
Total other comprehensive income (loss), (net of tax)	7,754	22,366	51,258	106,215
Total comprehensive income (pretax)	252,086	69,106	772,069	554,804
Total comprehensive income (tax effect)	(61,347)	(15,808)	(183,735)	(128,909)
Total comprehensive income (loss) (net of tax)	$ 190,739	$ 53,298	$ 588,334	$ 425,895