Accumulated Other Comprehensive Income (loss) (Table Text Block)	3 Months Ended
	Jun. 30, 2021
Table Text Block Supplement [Abstract]
Summary of accumulated other comprehensive income (loss) components, net of tax	Foreign Currency Translation   Unrealized Net Gain on Investments   Fair Market Value of Cash Flow Hedges   Postretirement Benefit Obligation Net Loss   Accumulated Other Comprehensive Income (Loss)     (Unaudited)     (In thousands) Balance at March 31, 2021 $ (52,929) $   167,653 $   (3,879) $   (3,988) $   106,857 Foreign currency translation   (3,392)   –   –   –   (3,392) Unrealized net losses on investments   –   (73,027)   –   –   (73,027) Change in fair value of cash flow hedges   –   –   (51)   –   (51) Amounts reclassified into earnings on hedging activities   –   –   745   –   745 Other comprehensive income (loss)   (3,392)   (73,027)   694   –   (75,725) Balance at June 30, 2021$( 56,321 )$  94,626 $ ( 3,185 )$ ( 3,988 )$  31,132