Marketable Securities (Schedule Of Marketable Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Marketable securities - Short-Term
Gain (Loss) on Investments [Line Items]
Cost	$ 6,151	$ 6,490
Unrealized Gains	0	5
Unrealized Losses	(8)	(2)
Fair Value	6,143	6,493
Marketable securities - Short-Term | U.S. government and agency obligations
Gain (Loss) on Investments [Line Items]
Cost	5,235	5,005
Unrealized Gains	0	4
Unrealized Losses	(7)	(1)
Fair Value	5,228	5,008
Marketable securities - Short-Term | Corporate debt securities and certificates of deposit
Gain (Loss) on Investments [Line Items]
Cost	916	1,476
Unrealized Gains	0	1
Unrealized Losses	(1)	(1)
Fair Value	915	1,476
Marketable securities - Short-Term | Asset backed securities
Gain (Loss) on Investments [Line Items]
Cost		9
Unrealized Gains		0
Unrealized Losses		0
Fair Value		9
Marketable securities - Long-Term
Gain (Loss) on Investments [Line Items]
Cost	9,292	8,750
Unrealized Gains	46	12
Unrealized Losses	(26)	(34)
Fair Value	9,312	8,728
Marketable securities - Long-Term | U.S. government and agency obligations
Gain (Loss) on Investments [Line Items]
Cost	4,143	4,815
Unrealized Gains	0	1
Unrealized Losses	(12)	(12)
Fair Value	4,131	4,804
Marketable securities - Long-Term | Corporate debt securities and certificates of deposit
Gain (Loss) on Investments [Line Items]
Cost	1,971	2,161
Unrealized Gains	1	0
Unrealized Losses	(9)	(17)
Fair Value	1,963	2,144
Marketable securities - Long-Term | Asset backed securities
Gain (Loss) on Investments [Line Items]
Cost	3,136	1,732
Unrealized Gains	1	0
Unrealized Losses	(5)	(5)
Fair Value	3,132	1,727
Marketable securities - Long-Term | Equity security
Gain (Loss) on Investments [Line Items]
Cost	42	42
Unrealized Gains	44	11
Unrealized Losses	0	0
Fair Value	$ 86	$ 53