Allowance for Credit Losses (Reserve Allowance for Various Credit Loss) (Details) $ in Thousands	6 Months Ended
	Sep. 30, 2021 USD ($)
Valuation And Qualifying Accounts [Abstract]
March 31, 2021	$ 4,656
Transition adjustment current expected credit losses	(602)
Write-offs against allowance	0
Recoveries	0
September 30, 2021	4,054
Trade Receivables
Valuation And Qualifying Accounts [Abstract]
March 31, 2021	2,835
Transition adjustment current expected credit losses	531
Write-offs against allowance	0
Recoveries	0
September 30, 2021	3,366
Investments, Fixed Maturities
Valuation And Qualifying Accounts [Abstract]
March 31, 2021	1,320
Transition adjustment current expected credit losses	(1,141)
Write-offs against allowance	0
Recoveries	0
September 30, 2021	179
Investments, Other
Valuation And Qualifying Accounts [Abstract]
March 31, 2021	501
Transition adjustment current expected credit losses	8
Write-offs against allowance	0
Recoveries	0
September 30, 2021	$ 509