Marketable Securities (Schedule Of Marketable Securities) (Details) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Marketable Securities - Short-Term [Member]
Gain (Loss) on Investments [Line Items]
Cost	$ 12,097,000	$ 10,628,000
Unrealized Gains	16,000	12,000
Unrealized Losses	(27,000)
Fair Value	12,086,000	10,640,000
Marketable Securities - Short-Term [Member] | US States Government And Agency Obligations [Member]
Gain (Loss) on Investments [Line Items]
Cost	7,050,000	6,495,000
Unrealized Gains	9,000	8,000
Unrealized Losses	(27,000)
Fair Value	7,032,000	6,503,000
Marketable Securities - Short-Term [Member] | Corporate Debt Securities And Certificates Of Deposit [Member]
Gain (Loss) on Investments [Line Items]
Cost	5,047,000	4,133,000
Unrealized Gains	7,000	4,000
Fair Value	5,054,000	4,137,000
Marketable Securities - Long-Term [Member]
Gain (Loss) on Investments [Line Items]
Cost	9,778,000	6,090,000
Unrealized Gains	30,000	37,000
Unrealized Losses	(70,000)	(21,000)
Fair Value	9,738,000	6,106,000
Marketable Securities - Long-Term [Member] | US States Government And Agency Obligations [Member]
Gain (Loss) on Investments [Line Items]
Cost	8,731,000	3,653,000
Unrealized Gains	27,000	28,000
Unrealized Losses	(23,000)	(1,000)
Fair Value	8,735,000	3,680,000
Marketable Securities - Long-Term [Member] | Corporate Debt Securities And Certificates Of Deposit [Member]
Gain (Loss) on Investments [Line Items]
Cost	798,000	2,353,000
Unrealized Gains	3,000	9,000
Unrealized Losses		(2,000)
Fair Value	801,000	2,360,000
Marketable Securities - Long-Term [Member] | Asset-backed Securities [Member]
Gain (Loss) on Investments [Line Items]
Cost	165,000
Fair Value	165,000
Marketable Securities - Long-Term [Member] | Equity Security [Member]
Gain (Loss) on Investments [Line Items]
Cost	84,000	84,000
Unrealized Losses	(47,000)	(18,000)
Fair Value	$ 37,000	$ 66,000