Marketable Securities (Schedule Of Marketable Securities) (Details) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Marketable Securities - Short-Term [Member]
Gain (Loss) on Investments [Line Items]
Cost	$ 10,620,000	$ 11,458,000
Unrealized Gains	13,000	15,000
Unrealized Losses		(35,000)
Fair Value	10,633,000	11,438,000
Marketable Securities - Short-Term [Member] | US States Government And Agency Obligations [Member]
Gain (Loss) on Investments [Line Items]
Cost	7,917,000	7,358,000
Unrealized Gains	10,000	10,000
Unrealized Losses		(35,000)
Fair Value	7,927,000	7,333,000
Marketable Securities - Short-Term [Member] | Corporate Debt Securities And Certificates Of Deposit [Member]
Gain (Loss) on Investments [Line Items]
Cost	2,703,000	4,100,000
Unrealized Gains	3,000	5,000
Fair Value	2,706,000	4,105,000
Marketable Securities - Long-Term [Member]
Gain (Loss) on Investments [Line Items]
Cost	10,034,000	10,432,000
Unrealized Gains	12,000	27,000
Unrealized Losses	(14,000)	(24,000)
Fair Value	10,032,000	10,435,000
Marketable Securities - Long-Term [Member] | US States Government And Agency Obligations [Member]
Gain (Loss) on Investments [Line Items]
Cost	6,936,000	9,033,000
Unrealized Gains	9,000	23,000
Unrealized Losses	(6,000)	(23,000)
Fair Value	6,939,000	9,033,000
Marketable Securities - Long-Term [Member] | Corporate Debt Securities And Certificates Of Deposit [Member]
Gain (Loss) on Investments [Line Items]
Cost	2,306,000	1,192,000
Unrealized Gains	2,000	4,000
Unrealized Losses	(7,000)	(1,000)
Fair Value	2,301,000	1,195,000
Marketable Securities - Long-Term [Member] | Asset-backed Securities [Member]
Gain (Loss) on Investments [Line Items]
Cost	750,000	165,000
Unrealized Losses	(1,000)
Fair Value	749,000	165,000
Marketable Securities - Long-Term [Member] | Equity Security [Member]
Gain (Loss) on Investments [Line Items]
Cost	42,000	42,000
Unrealized Gains	1,000
Fair Value	$ 43,000	$ 42,000