Investments (Table Text Block)

9 Months Ended

12 Months Ended

Dec. 31, 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	$	87,116	$	6,872	$	–	$	(80)	$	93,908
U.S. government agency mortgage-backed securities		28,935		1,940		(5)		(2)		30,868
Obligations of states and political subdivisions		159,596		15,829		(12)		(90)		175,323
Corporate securities		1,250,266		70,953		(4,404)		(1,411)		1,315,404
Mortgage-backed securities		42,665		1,214		–		(58)		43,821
Redeemable preferred stocks		14,640		492		–		(96)		15,036
Common stocks		17,970		8,261		(10)		–		26,221
	$	1,601,188	$	105,561	$	(4,431)	$	(1,737)	$	1,700,581

		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

		December 31, 2016				March 31, 2016
		Amortized Cost		Estimated Market Value		Amortized Cost		Estimated Market Value
		(Unaudited)
		(In thousands)
Due in one year or less	$	29,111	$	29,500	$	48,679	$	49,146
Due after one year through five years		319,439		334,064		250,576		256,597
Due after five years through ten years		604,645		639,749		557,984		557,961
Due after ten years		572,718		612,190		560,317		559,833
		1,525,913		1,615,503		1,417,556		1,423,537
Mortgage backed securities		42,665		43,821		42,991		43,404
Redeemable preferred stocks		14,640		15,036		17,977		18,428
Common stocks		17,970		26,221		17,732		25,169
	$	1,601,188	$	1,700,581	$	1,496,256	$	1,510,538