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Cash, Cash Equivalents And Marketable Securities (Narrative) (Details) (USD $)
3 Months Ended
Sep. 30, 2011
Mar. 31, 2011
Cash, Cash Equivalents and Marketable Securities [Line Items]  
Long-term marketable securities$ 26,528,000$ 27,880,000
Cumulative temporary decline in value of marketable securities2,100,000 
Cumulative temporary decline in value of marketable securities, net of tax1,300,000 
Valuation reserve112,000 
Valuation reserve, net of tax71,000 
Auction Rate Securities [Member]
  
Cash, Cash Equivalents and Marketable Securities [Line Items]  
Long-term marketable securities17,400,000 
Long-term marketable securities, face value19,500,000 
Long-term marketable securities, estimated market value$ 17,400,000 
Maximum [Member]
  
Cash, Cash Equivalents and Marketable Securities [Line Items]  
Period used as basis for computation of weighted average assumption period for reclassification of security to liquidity (months)55 
Minimum [Member]
  
Cash, Cash Equivalents and Marketable Securities [Line Items]  
Period used as basis for computation of weighted average assumption period for reclassification of security to liquidity (months)51