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Pension And Other Postretirement Benefit Plans (Components Of Company's Net Periodic Benefit Cost) (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 6 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Pension Benefits [Member]
        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 1,046 $ 1,274 $ 2,270 $ 2,564
Interest cost 3,153 3,386 6,319 6,837
Expected return on plan assets (3,197) (3,646) (6,694) (7,355)
Settlements 1,329 0 1,329 0
Net amortization and deferral 2,846 1,335 5,364 2,677
Net periodic benefit cost 5,177 2,349 8,588 4,723
Other Postretirement Benefits [Member]
        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 146 189 294 378
Interest cost 569 578 1,145 1,156
Expected return on plan assets (31) (34) (62) (68)
Settlements 0 0 0 0
Net amortization and deferral 48 (59) 100 (117)
Net periodic benefit cost $ 732 $ 674 $ 1,477 $ 1,349