Marketable Securities - Restricted (Unrealized losses on investments restricted from sale) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Total Number in Loss Position		5
Less than twelve months - fair values		$ 997
Less than twelve months - unrealized losses		(16)
Twelve months or greater - fair values		25,025
Twelve months or greater - unrealized losses		(369)
Total Fair Value		26,022
Total Unrealized Losses		(385)
Restricted Corporate Bonds [Member]
Total Number in Loss Position	1	1
Less than twelve months - fair values	508	2,075
Less than twelve months - unrealized losses	(3)	(14)
Twelve months or greater - fair values	0	0
Twelve months or greater - unrealized losses	0	0
Total Fair Value	508	2,075
Total Unrealized Losses	(3)	(14)
Total Restricted Available for Sale Securities [Member]
Total Number in Loss Position	1	1
Less than twelve months - fair values	508	2,075
Less than twelve months - unrealized losses	(3)	(14)
Twelve months or greater - fair values	0	0
Twelve months or greater - unrealized losses	0	0
Total Fair Value	508	2,075
Total Unrealized Losses	$ (3)	$ (14)