Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Less: Treasury Common Stock [Member]	Less: Treasury Preferred Stock [Member]	Nonvoting Common Stock [Member] Common Stock [Member]
Balance, beginning of period at Mar. 31, 2023	$ 6,504,191	$ 10,497	$ 453,643	$ 285,623	$ 7,003,148	$ 525,653	$ 151,997	$ 176
Cosolidated statement of change in equity
Foreign currency translation	469			469
Unrealized net gain (loss) on investments, net of tax	20,344			20,344
Change in fair value of cash flow hedges	3,842			3,842
Amounts reclassified into earnings on hedging activities, net	868			868
Net Income (Loss)	256,838				256,838
Series N Non-Voting Common Stock dividends paid	(7,059)				(7,059)
Net activity	273,566			23,787	249,779
Balance, end of period at Jun. 30, 2023	6,777,757	10,497	453,643	261,836	7,252,927	525,653	151,997	176
Balance, beginning of period at Mar. 31, 2024	7,172,445	10,497	462,548	223,216	7,600,090	525,653	151,997	176
Cosolidated statement of change in equity
Foreign currency translation	204			204
Unrealized net gain (loss) on investments, net of tax	5,413			5,413
Change in fair value of cash flow hedges	1,905			1,905
Amounts reclassified into earnings on hedging activities, net	1,075			1,075
Net Income (Loss)	195,417				195,417
Common stock dividends	(8,824)				(8,824)
Series N Non-Voting Common Stock dividends paid	(8,824)
Net activity	177,996			8,597	186,593
Balance, end of period at Jun. 30, 2024	$ 7,350,441	$ 10,497	$ 462,548	$ 231,813	$ 7,786,683	$ 525,653	$ 151,997	$ 176