Investments (Table Text Block)

9 Months Ended

Dec. 31, 2017

Investments Debt Equity Securities [Abstract]

Available-for-Sale Investments

Available-for-sale investments at December 31, 2017 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	$	123,695	$	3,529	$	(770)	$	(390)	$	126,064
U.S. government agency mortgage-backed securities		26,598		1,373		(1)		(5)		27,965
Obligations of states and political subdivisions		173,039		10,055		(148)		(81)		182,865
Corporate securities		1,351,074		51,228		(2,957)		(2,556)		1,396,789
Mortgage-backed securities		94,208		2,072		–		(100)		96,180
Redeemable preferred stocks		11,589		428		–		(31)		11,986
Common stocks		15,732		10,743		(10)		–		26,465
	$	1,795,935	$	79,428	$	(3,886)	$	(3,163)	$	1,868,314

Available-for-sale investments at March 31, 2017 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	$	123,474	$	2,892	$	–	$	(1,675)	$	124,691
U.S. government agency mortgage-backed securities		27,908		1,070		(6)		(377)		28,595
Obligations of states and political subdivisions		159,417		9,466		(23)		(424)		168,436
Corporate securities		1,263,703		32,901		(5,731)		(13,837)		1,277,036
Mortgage-backed securities		26,577		515		–		(5)		27,087
Redeemable preferred stocks		13,789		168		–		(468)		13,489
Common stocks		15,732		8,728		(10)		(16)		24,434
	$	1,630,600	$	55,740	$	(5,770)	$	(16,802)	$	1,663,768

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

The adjusted cost and estimated market value of available-for-sale investments by contractual maturity, were as follows:

		December 31, 2017				March 31, 2017
		Amortized Cost		Estimated Market Value		Amortized Cost		Estimated Market Value
		(Unaudited)
		(In thousands)
Due in one year or less	$	41,025	$	41,353	$	35,399	$	35,795
Due after one year through five years		396,559		408,603		324,286		333,016
Due after five years through ten years		611,026		631,009		598,232		607,184
Due after ten years		625,796		652,718		616,585		622,763
		1,674,406		1,733,683		1,574,502		1,598,758
Mortgage backed securities		94,208		96,180		26,577		27,087
Redeemable preferred stocks		11,589		11,986		13,789		13,489
Common stocks		15,732		26,465		15,732		24,434
	$	1,795,935	$	1,868,314	$	1,630,600	$	1,663,768