Marketable Securities (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Gain (Loss) on Investments [Line Items]
Maximum maturity of debt securities, years	3 years
Other-than-temporary impairment loss	$ 42,000
Net pre-tax unrealized gains (losses) for marketable securities	(17,000)	28,000
Maximum time for loss position, months	12 months	12 months
Proceeds from sale of marketable securities	3,154,000	3,175,000
Recognized gain from the sale of marketable securities	8,000
Marketable securities classified as cash equivalents, Recorded basis	2,824,000	685,000
Debt Securities Unrealized Gain Position [Member]
Gain (Loss) on Investments [Line Items]
Fair value	19,012,000	14,207,000
Unrealized gain	42,000	49,000
Debt Securities Unrealized Loss Position [Member]
Gain (Loss) on Investments [Line Items]
Fair value	2,819,000	2,473,000
Unrealized loss	(59,000)	(3,000)
Equity Security [Member]
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairment loss	42,000
Marketable Securities - Long-Term [Member]
Gain (Loss) on Investments [Line Items]
Fair value	10,435,000	6,106,000
Unrealized gain	27,000	37,000
Unrealized loss	(24,000)	(21,000)
Marketable Securities - Long-Term [Member] | Equity Security [Member]
Gain (Loss) on Investments [Line Items]
Fair value	42,000	66,000
Unrealized loss		$ (18,000)