Investments in Marketable Securities (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	$ 92,000	$ 127,000
Available-for-sale Securities, Gross Unrealized Gains	11,000	12,000
Letters of Credit Outstanding, Amount	2,600,000	3,100,000
Held-to-maturity Securities, Current	2,008,000	1,434,000
Held-to-maturity Securities, Noncurrent	1,788,000	3,841,000
Held-to-maturity Securities	3,796,000	5,275,000
Equity Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	44,000	65,000
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	48,000	62,000
Held-to-maturity Securities, Current	76,000	111,000
Held-to-maturity Securities, Noncurrent	0	0
Held-to-maturity Securities	76,000	111,000
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Current	1,051,000	1,323,000
Held-to-maturity Securities, Noncurrent	1,399,000	2,970,000
Held-to-maturity Securities	2,450,000	4,293,000
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Held-to-maturity Securities, Current	881,000	0
Held-to-maturity Securities, Noncurrent	389,000	871,000
Held-to-maturity Securities	$ 1,270,000	$ 871,000