Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2026	Mar. 31, 2025
Preferred stock:
Preferred stock, shares authorized	50,000,000	50,000,000
Debt Securities, Available-for-Sale [Abstract]
Available for sale investments, allowance for credit loss, net	$ 3,960	$ 3,104
Debt Securities, Available-for-Sale, Amortized Cost, Current	$ 2,558,342	$ 2,708,562
Voting Stock [Member]
Common stock:
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares, issued	41,985,700	41,985,700
Common stock, shares, outstanding	19,607,788	19,607,788
Common stock, par or stated value per share	$ 0.25	$ 0.25
Nonvoting Common Stock [Member]
Common stock:
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares, issued	176,470,092	176,470,092
Common stock, par or stated value per share	$ 0.001	$ 0.001
Common Stock in Treasury [Member]
Treasury stock:
Treasury Stock Common Shares	22,377,912	22,377,912
Preferred Stock in Treasury [Member]
Treasury stock:
Treasury Stock Common Shares	6,100,000	6,100,000