Earnings Per Share (Calculation of Basic and Diluted Earnings Per Share, Voting and Non Voting Common Stock) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2022	Dec. 31, 2021
Earnings Per Share Diluted Other Disclosures [Abstract]
Net earnings available to common shareholders	$ 199,244	$ 281,466	$ 885,261	$ 1,036,539
Voting Common Stock dividends declared	0	(9,804)	(19,608)	(29,412)
Non-Voting Common Stock dividends declared	$ (7,059)	$ 0	$ (7,059)	$ 0
Common Stock [Member]
Earnings Per Share Diluted Other Disclosures [Abstract]
Weighted average shares outstanding Common Stock	19,607,788	19,607,788	19,607,788	19,607,788
Percent Weighted Average Shares Outstanding Common Stock	10.00%	10.00%	10.00%	10.00%
Net earnings available to common shareholders	$ 0	$ 0	$ 0	$ 0
Undistributed earnings available to common stockholders	192,185	271,662	858,594	1,007,127
Undistributed earnings available to common stockholders, participating securities	$ 19,219	$ 27,166	$ 85,859	$ 100,713
Undistibuted earnings per share, common stock	$ 0.98	$ 1.39	$ 4.38	$ 5.14
Dividends declared per share, distributed	0	0.50	1.00	1.50
Basic and diluted earnings per share Common Stock	$ 0.98	$ 1.89	$ 5.38	$ 6.64
Nonvoting Common Stock [Member]
Earnings Per Share Diluted Other Disclosures [Abstract]
Weighted average shares outstanding Common Stock	176,470,092	176,470,092	176,470,092	176,470,092
Percent Weighted Average Shares Outstanding Common Stock	90.00%	90.00%	90.00%	90.00%
Net earnings available to common shareholders	$ 0	$ 0	$ 0	$ 0
Undistributed earnings available to common stockholders, participating securities	$ 172,967	$ 244,496	$ 772,735	$ 906,414
Undistibuted earnings per share, common stock	$ 0.98	$ 1.39	$ 4.38	$ 5.14
Dividends declared per share, distributed	0.04	0	0.04	0
Basic and diluted earnings per share Common Stock	$ 1.02	$ 1.39	$ 4.42	$ 5.14
Nonvoting Common Stock [Member] | Common Stock [Member]
Earnings Per Share Diluted Other Disclosures [Abstract]
Weighted average shares outstanding Common Stock	196,077,880	196,077,880	196,077,880	196,077,880