Accumulated Other Comprehensive Income (loss) (Table Text Block)	6 Months Ended
	Sep. 30, 2020
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, 2020 $ (47,235) $ 90,684 $ (6,196) $ (2,601) $ 34,652 Foreign currency translation   (2,627)   -   -   -   (2,627) Unrealized net gain on investments   -   45,340   -   -   45,340 Change in fair value of cash flow hedges   -   -   (497)   -   (497) Amounts reclassified into earnings on hedging activities   -   -   1,288   -   1,288 Other comprehensive income (loss)   (2,627)   45,340   791   -   43,504 Balance at September 30, 2020 $ (49,862) $ 136,024 $ (5,405) $ (2,601) $ 78,156