Investments (Table Text Block)	3 Months Ended
	Jun. 30, 2023
Investments Debt Equity Securities [Abstract]
Adjusted Cost and Estimated Market Value of Available-for-sale Investments	June 30, 2023   March 31, 2023     Amortized   Fair Value   Amortized   Fair Value     (Unaudited)         (In thousands) Due in one year or less $ 134,115 $ 130,997 $ 354,875 $ 354,184 Due after one year through five years   734,777   698,857   754,175   717,552 Due after five years through ten years   699,066   637,939   736,089   665,708 Due after ten years   740,801   631,066   790,568   654,201     2,308,759   2,098,859   2,635,707   2,391,645                   Mortgage-backed securities   359,413   308,367   370,880   317,392  $ 2,668,172 $ 2,407,226 $ 3,006,587 $ 2,709,037
Available for sale equity investments	June 30, 2023   March 31, 2023     Amortized   Fair Value   Amortized   Fair Value     (Unaudited)             (In thousands)                   Common stocks $ 29,613 $ 41,730 $ 29,577 $ 39,375 Non-redeemable preferred stocks   25,144   20,556   26,054   21,982  $ 54,757 $ 62,286 $ 55,631 $ 61,357
Other investments, carrying value	June 30,   March 31,     2023   2023     (Unaudited)         (In thousands)           Mortgage loans, net $ 510,307 $ 466,531 Short-term investments   13,490   15,921 Real estate   72,257   72,178 Policy loans   10,852   10,921 Other equity investments   13,234   9,989  $ 620,140 $ 575,540