Marketable Securities (Schedule Of Marketable Securities) (Details) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Marketable Securities - Short-Term [Member]
Gain (Loss) on Investments [Line Items]
Cost	$ 10,837,000	$ 10,628,000
Unrealized Gains	22,000	12,000
Fair Value	10,859,000	10,640,000
Marketable Securities - Short-Term [Member] | US States Government And Agency Obligations [Member]
Gain (Loss) on Investments [Line Items]
Cost	7,017,000	6,495,000
Unrealized Gains	17,000	8,000
Fair Value	7,034,000	6,503,000
Marketable Securities - Short-Term [Member] | Corporate Debt Securities And Certificates Of Deposit [Member]
Gain (Loss) on Investments [Line Items]
Cost	3,820,000	4,133,000
Unrealized Gains	5,000	4,000
Fair Value	3,825,000	4,137,000
Marketable Securities - Long-Term [Member]
Gain (Loss) on Investments [Line Items]
Cost	10,565,000	6,090,000
Unrealized Gains	38,000	37,000
Unrealized Losses	(37,000)	(21,000)
Fair Value	10,566,000	6,106,000
Marketable Securities - Long-Term [Member] | US States Government And Agency Obligations [Member]
Gain (Loss) on Investments [Line Items]
Cost	8,872,000	3,653,000
Unrealized Gains	33,000	28,000
Unrealized Losses	(1,000)	(1,000)
Fair Value	8,904,000	3,680,000
Marketable Securities - Long-Term [Member] | Corporate Debt Securities And Certificates Of Deposit [Member]
Gain (Loss) on Investments [Line Items]
Cost	1,609,000	2,353,000
Unrealized Gains	5,000	9,000
Unrealized Losses	(1,000)	(2,000)
Fair Value	1,613,000	2,360,000
Marketable Securities - Long-Term [Member] | Equity Security [Member]
Gain (Loss) on Investments [Line Items]
Cost	84,000	84,000
Unrealized Losses	(35,000)	(18,000)
Fair Value	$ 49,000	$ 66,000