Investments in Marketable Securities (Held to Maturity Securities, by Maturity) (Details) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Schedule of Held-to-maturity Securities [Line Items]
Available-for-sale Securities	$ 90,000	$ 127,000
Letters of Credit Outstanding, Amount	2,900,000	3,100,000
Held-to-maturity Securities, Current	2,616,000	1,434,000
Held-to-maturity Securities, Noncurrent	2,250,000	3,841,000
Held-to-maturity Securities, Total	4,866,000	5,275,000
Mutual Funds [Member]
Schedule of Held-to-maturity Securities [Line Items]
Available-for-sale Securities	42,000	65,000
Cash/Money Market Accounts [Member]
Schedule of Held-to-maturity Securities [Line Items]
Available-for-sale Securities	48,000	62,000
Held-to-maturity Securities, Current	52,000	111,000
Held-to-maturity Securities, Noncurrent	0	0
Held-to-maturity Securities, Total	52,000	111,000
US Treasury Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Current	2,128,000	1,323,000
Held-to-maturity Securities, Noncurrent	1,409,000	2,970,000
Held-to-maturity Securities, Total	3,537,000	4,293,000
US Government Agencies Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Current	436,000	0
Held-to-maturity Securities, Noncurrent	841,000	871,000
Held-to-maturity Securities, Total	$ 1,277,000	$ 871,000