Quarterly report pursuant to Section 13 or 15(d)

Investments in Marketable Securities (Held to Maturity Securities, by Maturity) (Details)

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Investments in Marketable Securities (Held to Maturity Securities, by Maturity) (Details) (USD $)
Mar. 31, 2013
Dec. 31, 2012
Schedule of Held-to-maturity Securities [Line Items]    
Available-for-sale Securities $ 92,000 $ 92,000
Letters of Credit Outstanding, Amount 2,200,000 2,600,000
Held-to-maturity Securities, Current 2,900,000 2,008,000
Held-to-maturity Securities, Noncurrent 907,000 1,788,000
Held-to-maturity Securities, Total 3,807,000 3,796,000
Mutual Funds [Member]
    
Schedule of Held-to-maturity Securities [Line Items]    
Available-for-sale Securities 44,000 44,000
Cash/Money Market Accounts [Member]
    
Schedule of Held-to-maturity Securities [Line Items]    
Available-for-sale Securities 48,000 48,000
Held-to-maturity Securities, Current 111,000 76,000
Held-to-maturity Securities, Noncurrent 0 0
Held-to-maturity Securities, Total 111,000 76,000
US Treasury Securities [Member]
    
Schedule of Held-to-maturity Securities [Line Items]    
Held-to-maturity Securities, Current 1,914,000 1,051,000
Held-to-maturity Securities, Noncurrent 520,000 1,399,000
Held-to-maturity Securities, Total 2,434,000 2,450,000
US Government Agencies Securities [Member]
    
Schedule of Held-to-maturity Securities [Line Items]    
Held-to-maturity Securities, Current 875,000 881,000
Held-to-maturity Securities, Noncurrent 387,000 389,000
Held-to-maturity Securities, Total $ 1,262,000 $ 1,270,000