Financial Instruments And Investments (Marketable Securities Fair Value And Unrealized Losses) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2011		Dec. 31, 2010
Marketable Securities Fair Value Less than 12 Months	$ 26,785		$ 33,816	[1]
Marketable Securities Fair Value 12 Months or Longer	8,194		8,507	[1]
Marketable Securities Fair Value Total	34,979		42,323	[1]
Marketable Securities Unrealized Losses Less than 12 Months	(1,348)		(1,245)	[1]
Marketable Securities Unrealized Losses 12 Months or Longer	(859)		(592)	[1]
Marketable Securities Unrealized Losses Total	(2,207)		(1,837)	[1]
Number of investable securities	82		96
Total Debt Securities [Member]
Marketable Securities Fair Value Less than 12 Months	21,405		26,873	[1]
Marketable Securities Fair Value 12 Months or Longer	4,723		4,204	[1]
Marketable Securities Fair Value Total	26,128		31,077	[1]
Marketable Securities Unrealized Losses Less than 12 Months	(315)		(471)	[1]
Marketable Securities Unrealized Losses 12 Months or Longer	(194)		(172)	[1]
Marketable Securities Unrealized Losses Total	(509)		(643)	[1]
Corporate Obligations [Member]
Marketable Securities Fair Value Less than 12 Months	2,915	[2]	1,855	[1]
Marketable Securities Fair Value 12 Months or Longer	93	[2]	0	[1]
Marketable Securities Fair Value Total	3,008	[2]	1,855	[1]
Marketable Securities Unrealized Losses Less than 12 Months	(68)	[2]	(18)	[1]
Marketable Securities Unrealized Losses 12 Months or Longer	(3)	[2]	0	[1]
Marketable Securities Unrealized Losses Total	(71)	[2]	(18)	[1]
Federal Agency Mortgage Backed Securities [Member]
Marketable Securities Fair Value Less than 12 Months	3,283		2,290	[1]
Marketable Securities Fair Value 12 Months or Longer	0		441	[1]
Marketable Securities Fair Value Total	3,283		2,731	[1]
Marketable Securities Unrealized Losses Less than 12 Months	(48)		(51)	[1]
Marketable Securities Unrealized Losses 12 Months or Longer	0		(27)	[1]
Marketable Securities Unrealized Losses Total	(48)		(78)	[1]
Municipal Obligations [Member]
Marketable Securities Fair Value Less than 12 Months	6,532	[2]	13,145	[1]
Marketable Securities Fair Value 12 Months or Longer	4,228	[2]	3,763	[1]
Marketable Securities Fair Value Total	10,760	[2]	16,908	[1]
Marketable Securities Unrealized Losses Less than 12 Months	(92)	[2]	(278)	[1]
Marketable Securities Unrealized Losses 12 Months or Longer	(190)	[2]	(145)	[1]
Marketable Securities Unrealized Losses Total	(282)	[2]	(423)	[1]
Common Stock [Member]
Marketable Securities Fair Value Less than 12 Months	5,380	[2]	6,943	[1]
Marketable Securities Fair Value 12 Months or Longer	3,471	[2]	4,303	[1]
Marketable Securities Fair Value Total	8,851	[2]	11,246	[1]
Marketable Securities Unrealized Losses Less than 12 Months	(1,033)	[2]	(774)	[1]
Marketable Securities Unrealized Losses 12 Months or Longer	(665)	[2]	(420)	[1]
Marketable Securities Unrealized Losses Total	(1,698)	[2]	(1,194)	[1]
U.S. Government Bonds [Member]
Marketable Securities Fair Value Less than 12 Months	8,675	[2]	9,583	[1]
Marketable Securities Fair Value 12 Months or Longer	402	[2]	0	[1]
Marketable Securities Fair Value Total	9,077	[2]	9,583	[1]
Marketable Securities Unrealized Losses Less than 12 Months	(107)	[2]	(124)	[1]
Marketable Securities Unrealized Losses 12 Months or Longer	(1)	[2]	0	[1]
Marketable Securities Unrealized Losses Total	$ (108)	[2]	$ (124)	[1]

[1] Includes approximately 96 securities.

[2] Includes approximately 82 securities.