Investments (Table Text Block)	9 Months Ended	12 Months Ended
	Dec. 31, 2022	Mar. 31, 2022
Investments Debt Equity Securities [Abstract]
Available-for-Sale Investments	Amortized   Gross   Gross   Gross   Allowance for Expected Credit Losses   Estimated     (Unaudited)     (In thousands) U.S. treasury securities and government obligations $ 353,331 $   582 $   (3,844) $   (7,761) $   – $   342,308 U.S. government agency mortgage-backed securities   34,920   58   (6,263)   (602)   –   28,113 Obligations of states and political subdivisions   164,547   503   (3,458)   (10,609)   –   150,983 Corporate securities   2,060,503   790   (39,556)   (210,257)   (2,243)   1,809,237 Mortgage-backed securities   375,819   30   –   (42,962)   –   332,887  $ 2,989,120 $  1,963 $ ( 53,121 )$ ( 272,191 )$ ( 2,243 )$  2,663,528	Amortized   Gross   Gross   Gross   Allowance for Expected Credit Losses   Estimated           (In thousands) U.S. treasury securities and government obligations $ 128,078 $   7,984 $   – $   (969) $   – $   135,093 U.S. government agency mortgage-backed securities   44,678   280   (42)   (3,111)   –   41,805 Obligations of states and political subdivisions   178,040   15,450   –   (508)   –   192,982 Corporate securities   1,989,212   138,909   (402)   (6,604)   (60)   2,121,055 Mortgage-backed securities   324,029   7,671   (1)   (1,542)   –   330,157  $ 2,664,037 $  170,294 $ ( 445 )$ ( 12,734 )$ ( 60 )$  2,821,092
Adjusted Cost and Estimated Market Value of Available-for-sale Investments	December 31, 2022   March 31, 2022     Amortized   Estimated   Amortized   Estimated     (Unaudited)         (In thousands) Due in one year or less $ 333,984 $ 333,803 $ 97,969 $ 99,432 Due after one year through five years   602,861   575,794   541,840   570,135 Due after five years through ten years   756,691   674,055   704,295   765,073 Due after ten years   919,765   746,989   995,904   1,056,295     2,613,301   2,330,641   2,340,008   2,490,935                   Mortgage-backed securities   375,819   332,887   324,029   330,157  $ 2,989,120 $ 2,663,528 $ 2,664,037 $ 2,821,092
Available for sale equity investments	December 31, 2022   March 31, 2022     Amortized   Estimated   Amortized   Estimated     (Unaudited)             (In thousands)                   Common stocks $ 29,686 $ 37,619 $ 27,674 $ 46,212 Non-redeemable preferred stocks   26,054   22,054   26,054   26,095  $ 55,740 $ 59,673 $ 53,728 $ 72,307
Carrying value of Investments, other	December 31,   March 31,     2022   2022     (Unaudited)         (In thousands)           Mortgage loans, net $ 414,886 $ 423,163 Short-term investments   13,306   30,916 Real estate   71,707   67,824 Policy loans   10,680   10,309 Other equity investments   7,876   11,543  $ 518,455 $ 543,755