Investments in Marketable Securities (Held to Maturity Securities, by Maturity) (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Schedule of Held-to-maturity Securities [Line Items]
Short-term Investments	$ 1,349,000
Available-for-sale Securities	96,000	92,000
Letters of Credit Outstanding, Amount	2,000,000	2,600,000
Held-to-maturity Securities, Current	2,236,000	2,008,000
Held-to-maturity Securities, Noncurrent	0	1,788,000
Held-to-maturity Securities, Total	2,236,000	3,796,000
Long-term Investments	887,000
Mutual Funds [Member]
Schedule of Held-to-maturity Securities [Line Items]
Available-for-sale Securities	48,000	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	44,000	76,000
Held-to-maturity Securities, Noncurrent	0	0
Held-to-maturity Securities, Total	44,000	76,000
US Treasury Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Current	1,370,000	1,051,000
Held-to-maturity Securities, Noncurrent	0	1,399,000
Held-to-maturity Securities, Total	1,370,000	2,450,000
US Government Agencies Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity Securities, Current	822,000	881,000
Held-to-maturity Securities, Noncurrent	0	389,000
Held-to-maturity Securities, Total	$ 822,000	$ 1,270,000