Investments (Table Text Block)

6 Months Ended

12 Months Ended

Sep. 30, 2016

Mar. 31, 2016

Investments Debt Equity Securities [Abstract]

Available-for-Sale Investments

		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	$	73,751	$	7,216	$	–	$	–	$	80,967
U.S. government agency mortgage-backed securities		29,902		2,116		(6)		(2)		32,010
Obligations of states and political subdivisions		161,620		16,285		(11)		–		177,894
Corporate securities		1,198,017		67,183		(7,775)		(3,266)		1,254,159
Mortgage-backed securities		42,765		1,238		–		(38)		43,965
Redeemable preferred stocks		15,332		795		–		(127)		16,000
Common stocks		17,970		9,482		(10)		(17)		27,425
	$	1,539,357	$	104,315	$	(7,802)	$	(3,450)	$	1,632,420

		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	$	85,861	$	3,791	$	–	$	(193)	$	89,459
U.S. government agency mortgage-backed securities		21,845		1,596		(6)		(39)		23,396
Obligations of states and political subdivisions		166,725		10,660		(81)		(414)		176,890
Corporate securities		1,143,125		26,861		(8,013)		(28,181)		1,133,792
Mortgage-backed securities		42,991		475		–		(62)		43,404
Redeemable preferred stocks		17,977		556		–		(105)		18,428
Common stocks		17,732		7,822		(10)		(375)		25,169
	$	1,496,256	$	51,761	$	(8,110)	$	(29,369)	$	1,510,538

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

		September 30, 2016				March 31, 2016
		Amortized Cost		Estimated Market Value		Amortized Cost		Estimated Market Value
		(Unaudited)
		(In thousands)
Due in one year or less	$	29,344	$	29,790	$	48,679	$	49,146
Due after one year through five years		316,614		330,006		250,576		256,597
Due after five years through ten years		570,836		602,486		557,984		557,961
Due after ten years		546,496		582,748		560,317		559,833
		1,463,290		1,545,030		1,417,556		1,423,537
Mortgage backed securities		42,765		43,965		42,991		43,404
Redeemable preferred stocks		15,332		16,000		17,977		18,428
Common stocks		17,970		27,425		17,732		25,169
	$	1,539,357	$	1,632,420	$	1,496,256	$	1,510,538