Investments (Table Text Block)

6 Months Ended

Sep. 30, 2018

Investments Debt Equity Securities [Abstract]

Available-for-Sale Investments

Available-for-sale investments as of September 30, 2018 were as follows:

		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses More than 12 Months		Gross Unrealized Losses Less than 12 Months		Estimated Market Value
		(Unaudited)
		(In thousands)
U.S. treasury securities and government obligations	$	125,462	$	1,394	$	(1,688)	$	(1,541)	$	123,627
U.S. government agency mortgage-backed securities		62,273		628		(2)		(981)		61,918
Obligations of states and political subdivisions		204,297		6,623		(229)		(495)		210,196
Corporate securities		1,497,362		17,605		(5,695)		(27,178)		1,482,094
Mortgage-backed securities		101,647		709		–		(1,027)		101,329
Redeemable preferred stocks		1,493		63		–		–		1,556
	$	1,992,534	$	27,022	$	(7,614)	$	(31,222)	$	1,980,720

Available-for-sale investments as of March 31, 2018 were as follows:

		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses More than 12 Months		Gross Unrealized Losses Less than 12 Months		Estimated Market Value
		(In thousands)
U.S. treasury securities and government obligations	$	123,557	$	3,595	$	(1,036)	$	(203)	$	125,913
U.S. government agency mortgage-backed securities		36,416		951		(1)		(93)		37,273
Obligations of states and political subdivisions		178,702		9,938		(217)		(18)		188,405
Corporate securities		1,388,300		50,056		(3,009)		(1,826)		1,433,521
Mortgage-backed securities		94,106		2,072		–		(153)		96,025
Redeemable preferred stocks		2,118		129		–		–		2,247
	$	1,823,199	$	66,741	$	(4,263)	$	(2,293)	$	1,883,384

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

		September 30, 2018				March 31, 2018
		Amortized Cost		Estimated Market Value		Amortized Cost		Estimated Market Value
		(Unaudited)
		(In thousands)
Due in one year or less	$	54,102	$	54,349	$	36,446	$	36,674
Due after one year through five years		489,499		489,545		441,223		450,816
Due after five years through ten years		625,687		619,371		607,895		626,174
Due after ten years		720,106		714,570		641,411		671,448
		1,889,394		1,877,835		1,726,975		1,785,112
Mortgage backed securities		101,647		101,329		94,106		96,025
Redeemable preferred stocks		1,493		1,556		2,118		2,247
	$	1,992,534	$	1,980,720	$	1,823,199	$	1,883,384