Fair Value Measurements (Table Text Block)	6 Months Ended	12 Months Ended
	Sep. 30, 2021	Mar. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Financial Instruments, Carrying and Estimated fair values	Fair Value Hierarchy     Carrying               Total Estimated As of September 30, 2021   Value   Level 1   Level 2   Level 3   Fair Value     (Unaudited) Assets   (In thousands) Reinsurance recoverables and trade receivables, net $ 227,935 $ – $ – $ 227,935 $ 227,935 Mortgage loans, net   471,566   –   –   471,566   471,566 Other investments   100,376   –   –   100,376   100,376 Total $ 799,877 $ – $ – $ 799,877 $ 799,877                                             Liabilities                     Notes, loans and finance leases payable   5,364,279   –   5,364,279   –   5,127,100 Total$ 5,364,279 $ – $ 5,364,279 $ – $ 5,127,100	Fair Value Hierarchy     Carrying               Total Estimated As of March 31, 2021   Value   Level 1   Level 2   Level 3   Fair Value     (In thousands) Assets                     Reinsurance recoverables and trade receivables, net $ 224,426 $ – $ – $ 224,426 $ 224,426 Mortgage loans, net   391,230   –   –   391,230   391,230 Other investments   98,529   –   –   98,529   98,529 Total $ 714,185 $ – $ – $ 714,185 $ 714,185                                             Liabilities                     Notes, loans and finance leases payable   4,698,615   –   4,698,615   –   4,449,691 Total$ 4,698,615 $ – $ 4,698,615 $ – $ 4,449,691
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis	As of September 30, 2021   Total   Level 1   Level 2   Level 3     (Unaudited) Assets   (In thousands) Short-term investments $ 2,215,846 $ 2,215,846 $ – $ – Fixed maturities - available for sale   2,790,243   6,721   2,783,407   115 Preferred stock   30,176   30,176   –   – Common stock   24,728   24,728   –   – Derivatives   5,754   5,754   –   – Total $ 5,066,747 $ 2,283,225 $ 2,783,407 $ 115                                     Liabilities                 Derivatives   3,292   –   3,292   – Total $ 3,292 $ – $ 3,292 $ – As of March 31, 2021   Total   Level 1   Level 2   Level 3     (In thousands) Assets                 Short-term investments $ 839,250 $ 839,250 $ – $ – Fixed maturities - available for sale   2,653,539   6,967   2,646,415   157 Preferred stock   21,677   21,677   –   – Common stock   20,440   20,440   –   – Derivatives   6,601   6,601   –   – Total $ 3,541,507 $ 894,935 $ 2,646,415 $ 157                                     Liabilities                 Derivatives   5,141   –   5,141   – Total$ 5,141 $ – $ 5,141 $ –