Investments (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ 9,701,000	$ (5,676,000)	$ 6,170,000	$ (5,252,000)
Investment in Marketable Securities (Textual) [Abstract]
Other comprehensive unrealized gain	17.2
Marketable Securities, Unrealized Gain (Loss)	(7,491,000)	(5,676,000)	(11,057,000)	(5,252,000)
Short term investments	0		0		999,000
Marketable securities [Member]
Available-for-sale Securities
Available-for-sale Securities, Amortized Cost	17,608,000		17,608,000		34,786,000
Available-for-sales Securities, Gross Unrealized Losses	(1,799,000)		(1,799,000)		(10,443,000)
Available-for-sale Securities, Gross Unrealized Gains	199,000		199,000		2,722,000
Available-for-sale Securities, Estimated Fair Value	$ 16,008,000		$ 16,008,000		$ 27,065,000