Policy Benefits And Losses Claims And Loss Expenses Payable (Present Value Expected Future Policy Benefits) (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2021
Liability For Future Policy Benefit Expected Future Policy Benefit [Roll Forward]
Payout annuities and market risk benefits	$ 2,363,143		$ 2,398,884
Life and annuity ICOS and IBNR / Reinsurance losses payable					$ 41,438
End of period balance, Oxford	373,100
Policy benefit and losses, claims and loss expense balance, end of period	838,945		880,202
Life Insurance [Member]
Liability For Future Policy Benefit Expected Future Policy Benefit [Roll Forward]
Balance, beginning of year	741,037	$ 971,882	971,882
Beginning balance at original discount rate	760,198	821,286	821,286
Effect of actual variances from expected experience	10,149		10,271	$ 1,901
Adjusted beginning of year balance			749,927	823,187
Issuances	6,824	16,555
Interest accrual	26,350	28,791
Net premium collected	62,401	69,475
Ending balance at original discount rate	720,700	799,058	760,198	821,286
Effect of changes in discount rate assumptions (AOCI)	39,847	31,386
Balance, end of the year	680,853	767,672	741,037	971,882
End of period, LFPB, net	308,467	318,003
Payout annuities and market risk benefits	31,048	33,049
Life and annuity ICOS and IBNR / Reinsurance losses payable	9,556	10,387
Life DPL/Other life and health	23,724	35,276
End of period balance, Oxford	373,069	397,166
Balance, Moving and Storage	317,409	342,645
Balance, Property and Casualty	148,467	156,259
Policy benefit and losses, claims and loss expense balance, end of period	838,945	896,070
Life Insurance Segment [Member] | Oxford
Liability For Future Policy Benefit Expected Future Policy Benefit [Roll Forward]
Balance, beginning of year	530,983	672,254	672,254
Beginning balance at original discount rate	533,688	552,109	552,109
Effect of actual variances from expected experience			584	150
Adjusted beginning of year balance			532,067	551,959
Issuances	6,746	14,101
Interest accrual	19,830	20,654
Net premium collected	39,544	43,602
Ending balance at original discount rate	519,099	543,112	533,688	552,109
Effect of changes in discount rate assumptions (AOCI)	19,397	9,514
Balance, end of the year	499,702	533,598	530,983	672,254
Health Insurance Product Line [Member]
Liability For Future Policy Benefit Expected Future Policy Benefit [Roll Forward]
Life and annuity ICOS and IBNR / Reinsurance losses payable					$ 0
Health Insurance Product Line [Member] | Oxford
Liability For Future Policy Benefit Expected Future Policy Benefit [Roll Forward]
Balance, beginning of year	210,054	299,628	299,628
Beginning balance at original discount rate	226,510	269,177	269,177
Effect of actual variances from expected experience			9,565	2,051
Adjusted beginning of year balance			217,860	271,228
Issuances	78	2,454
Interest accrual	6,520	8,137
Net premium collected	22,857	25,873
Ending balance at original discount rate	201,601	255,946	226,510	269,177
Effect of changes in discount rate assumptions (AOCI)	20,450	21,872
Balance, end of the year	$ 181,151	$ 234,074	$ 210,054	$ 299,628