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 ($)
Sep. 30, 2015
Dec. 31, 2014
Schedule of Held-to-maturity Securities [Line Items]    
Available-for-sale Securities $ 108,000 $ 107,000
Letters of Credit Outstanding, Amount 1,100,000 1,400,000
Held-to-maturity Securities, Current 341,000 534,000
Held-to-maturity Securities, Noncurrent 1,248,000 1,057,000
Held-to-maturity Securities, Total 1,589,000 1,591,000
Mutual Funds [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Available-for-sale Securities 60,000 59,000
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 105,000 204,000
Held-to-maturity Securities, Noncurrent 0 0
Held-to-maturity Securities, Total 105,000 204,000
US Treasury Securities [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held-to-maturity Securities, Current 110,000 105,000
Held-to-maturity Securities, Noncurrent 1,117,000 965,000
Held-to-maturity Securities, Total 1,227,000 1,070,000
US Government Agencies Securities [Member]    
Schedule of Held-to-maturity Securities [Line Items]    
Held-to-maturity Securities, Current 126,000 225,000
Held-to-maturity Securities, Noncurrent 131,000 92,000
Held-to-maturity Securities, Total $ 257,000 $ 317,000