Marketable Securities (Schedule Of Marketable Securities) (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Marketable Securities - Short-Term [Member]
Gain (Loss) on Investments [Line Items]
Cost	$ 11,458,000	$ 10,628,000
Unrealized Gains	15,000	12,000
Unrealized Losses	(35,000)
Fair Value	11,438,000	10,640,000
Marketable Securities - Short-Term [Member] | US States Government And Agency Obligations [Member]
Gain (Loss) on Investments [Line Items]
Cost	7,358,000	6,495,000
Unrealized Gains	10,000	8,000
Unrealized Losses	(35,000)
Fair Value	7,333,000	6,503,000
Marketable Securities - Short-Term [Member] | Corporate Debt Securities And Certificates Of Deposit [Member]
Gain (Loss) on Investments [Line Items]
Cost	4,100,000	4,133,000
Unrealized Gains	5,000	4,000
Fair Value	4,105,000	4,137,000
Marketable Securities - Long-Term [Member]
Gain (Loss) on Investments [Line Items]
Cost	10,432,000	6,090,000
Unrealized Gains	27,000	37,000
Unrealized Losses	(24,000)	(21,000)
Fair Value	10,435,000	6,106,000
Marketable Securities - Long-Term [Member] | US States Government And Agency Obligations [Member]
Gain (Loss) on Investments [Line Items]
Cost	9,033,000	3,653,000
Unrealized Gains	23,000	28,000
Unrealized Losses	(23,000)	(1,000)
Fair Value	9,033,000	3,680,000
Marketable Securities - Long-Term [Member] | Corporate Debt Securities And Certificates Of Deposit [Member]
Gain (Loss) on Investments [Line Items]
Cost	1,192,000	2,353,000
Unrealized Gains	4,000	9,000
Unrealized Losses	(1,000)	(2,000)
Fair Value	1,195,000	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	42,000	84,000
Unrealized Losses		(18,000)
Fair Value	$ 42,000	$ 66,000