Marketable Securities (Summary Of Marketable Securities Treated As Available-For-Sale Securities) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities, Amortized cost	$ 27,054	$ 27,048	$ 30,594
Total available-for-sale securities, Gross unrealized gains	150	123	174
Total available-for-sale securities, Gross unrealized losses	(10)	(6)	(12)
Total available-for-sale securities, Fair value	27,194	27,165	30,756
Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities, Amortized cost	197	197	183
Total available-for-sale securities, Gross unrealized gains	150	123	154
Total available-for-sale securities, Gross unrealized losses	0	0	0
Total available-for-sale securities, Fair value	347	320	337
State And Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities, Amortized cost			4,560
Total available-for-sale securities, Gross unrealized gains			0
Total available-for-sale securities, Gross unrealized losses			(12)
Total available-for-sale securities, Fair value			4,548
Government And Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities, Amortized cost	26,857	26,851	25,851
Total available-for-sale securities, Gross unrealized gains	0	0	20
Total available-for-sale securities, Gross unrealized losses	(10)	(6)	0
Total available-for-sale securities, Fair value	$ 26,847	$ 26,845	$ 25,871