Investments (Table Text Block)

6 Months Ended

12 Months Ended

Sep. 30, 2024

Mar. 31, 2024

Investments Debt Equity Securities [Abstract]

Available for sale investments

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Allowance for Expected Credit Losses			Fair Value
	(Unaudited)
	(In thousands)
U.S. treasury securities and government obligations	$	150,029	$	208	$	(9,348	)	$	—		$	140,889
U.S. government agency mortgage-backed securities		45,374		107		(8,255	)		—			37,226
Obligations of states and political subdivisions		142,067		197		(9,098	)		—			133,166
Corporate securities		1,943,081		1,271		(171,608	)		(2,814	)		1,769,930
Mortgage-backed securities		402,279		150		(45,717	)		—			356,712
	$	2,682,830	$	1,933	$	(244,026	)	$	(2,814	)	$	2,437,923

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Allowance for Expected Credit Losses			Fair Value
	(Unaudited)
	(In thousands)
U.S. treasury securities and government obligations	$	191,070	$	2,123	$	(8,921	)	$	—		$	184,272
U.S. government agency mortgage-backed securities		48,067		250		(7,664	)		—			40,653
Obligations of states and political subdivisions		151,197		918		(7,533	)		—			144,582
Corporate securities		1,963,249		2,762		(152,799	)		(1,052	)		1,812,160
Mortgage-backed securities		306,510		34		(45,707	)		—			260,837
	$	2,660,093	$	6,087	$	(222,624	)	$	(1,052	)	$	2,442,504

Available for sale investments, unrealized losses, fair value

	September 30, 2024
	Less than or equal to 1 year					Greater than 1 year					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
	(Unaudited)
	(In thousands)
U.S. treasury securities and government obligations	$	39,648	$	(35	)	$	97,088	$	(9,313	)	$	136,736	$	(9,348	)
U.S. government agency mortgage-backed securities		—		—			22,087		(8,255	)		22,087		(8,255	)
Obligations of states and political subdivisions		37,607		(676	)		79,068		(8,422	)		116,675		(9,098	)
Corporate securities		208,344		(1,953	)		1,475,083		(169,655	)		1,683,427		(171,608	)
Mortgage-backed securities		58,938		(177	)		234,037		(45,540	)		292,975		(45,717	)
	$	344,537	$	(2,841	)	$	1,907,363	$	(241,185	)	$	2,251,900	$	(244,026	)

	March 31, 2024
	Less than or equal to 1 year					Greater than 1 year					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
	(Unaudited)
	(In thousands)
U.S. treasury securities and government obligations	$	1,888	$	(13	)	$	103,336	$	(8,908	)	$	105,224	$	(8,921	)
U.S. government agency mortgage-backed securities		—		—			23,711		(7,664	)		23,711		(7,664	)
Obligations of states and political subdivisions		10,492		(222	)		80,082		(7,311	)		90,574		(7,533	)
Corporate securities		132,513		(1,258	)		1,495,167		(151,541	)		1,627,680		(152,799	)
Mortgage-backed securities		3,008		(23	)		248,423		(45,684	)		251,431		(45,707	)
	$	147,901	$	(1,516	)	$	1,950,719	$	(221,108	)	$	2,098,620	$	(222,624	)

Gross proceeds from matured or redeemed securities were $200.8 million and $405.2 million for the first six months ended September 30, 2024 and September 30, 2023, respectively. Included in the September 30, 2024 and 2023 proceeds were $73.0 million and $225.0 million from the Moving and Storage Treasuries that matured. The gross realized gains on these sales totaled $2.1 million and $1.5 million during the first six months of fiscal 2025 and 2024, respectively. The gross realized losses on these sales totaled $0.3 million and $1.1 million during the first six months of fiscal 2025 and 2024, respectively.

For available-for-sale debt securities in an unrealized loss position, we first assess whether the security is below investment grade. For securities that are below investment grade, we evaluate whether the decline in fair value has resulted from credit losses or other factors such as the interest rate environment. Declines in value due to credit are recognized as an allowance. In making this assessment, management considers the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency, and adverse market conditions specifically related to the security, among other factors. If this assessment indicates that a credit loss exists, cumulative default rates based on ratings are used to determine the potential cost of default, by year. The present value of these potential costs is then compared to the amortized cost of the security to determine the credit loss, limited by the amount that the fair value is less than the amortized cost basis.

Declines in fair value that have not been recorded through an allowance for credit losses, such as declines due to changes in market interest rates, are recorded through accumulated other comprehensive income, net of applicable taxes. If we intend to sell a security, or it is more likely than not that we will be required to sell the security before recovery of its amortized cost basis, the security is written down to its fair value and the write down is charged against the allowance for credit losses, with any incremental impairment reported in earnings. Reversals of the allowance for credit losses are permitted and should not exceed the allowance amount initially recognized.

Changes in the allowance for credit losses are recorded as provision for (or reversal of) credit loss expense. There was a $1.8 million and ($0.4) million net impairment charge recorded in the first six months ended September 30, 2024 and 2023, respectively.

Expected maturities may differ from contractual maturities as borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.

Adjusted Cost and Estimated Market Value of Available-for-sale Investments

	September 30, 2024				March 31, 2024
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
	(Unaudited)
	(In thousands)
Due in one year or less	$	274,397	$	272,854	$	266,357	$	266,578
Due after one year through five years		645,371		623,920		748,338		723,903
Due after five years through ten years		614,127		554,516		614,890		564,422
Due after ten years		746,656		629,921		723,998		626,764
		2,280,551		2,081,211		2,353,583		2,181,667
Mortgage-backed securities		402,279		356,712		306,510		260,837
	$	2,682,830	$	2,437,923	$	2,660,093	$	2,442,504

	September 30, 2024				March 31, 2024
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
	(Unaudited)
	(In thousands)
Due in one year or less	$	274,397	$	272,854	$	266,357	$	266,578
Due after one year through five years		645,371		623,920		748,338		723,903
Due after five years through ten years		614,127		554,516		614,890		564,422
Due after ten years		746,656		629,921		723,998		626,764
		2,280,551		2,081,211		2,353,583		2,181,667
Mortgage-backed securities		402,279		356,712		306,510		260,837
	$	2,682,830	$	2,437,923	$	2,660,093	$	2,442,504

Available for sale equity investments

Equity investments of common stock and non-redeemable preferred stock were as follows:

	September 30, 2024				March 31, 2024
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
	(Unaudited)
	(In thousands)
Common stocks	$	29,422	$	41,529	$	29,604	$	45,014
Non-redeemable preferred stocks		25,144		21,766		25,144		21,260
	$	54,566	$	63,295	$	54,748	$	66,274

Equity investments of common stock and non-redeemable preferred stock were as follows:

	September 30, 2024				March 31, 2024
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
	(Unaudited)
	(In thousands)
Common stocks	$	29,422	$	41,529	$	29,604	$	45,014
Non-redeemable preferred stocks		25,144		21,766		25,144		21,260
	$	54,566	$	63,295	$	54,748	$	66,274

Carrying value of Investments, other

The carrying value of the other investments was as follows:

	September 30,		March 31,
	2024		2024
	(Unaudited)
	(In thousands)
Mortgage loans, net	$	623,042	$	604,481
Short-term investments		—		997
Policy loans		11,642		11,229
Other investments		9,209		17,229
	$	643,893	$	633,936