Investments (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Short-term Investments [Member]	Mar. 31, 2014 Marketable securities [Member]	Dec. 31, 2013 Marketable securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax	$ 600,000
Available-for-sale Securities
Cost			45,724,000	15,484,000	17,649,000
Gross Unrealized Losses			(96,000)	(724,000)	(3,300,000)
Gross Unrealized Gains			0	886,000	172,000
Available-for-sale Securities, Estimated Fair Value			45,628,000	15,646,000	14,521,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Unrealized Losses Total			(96,000)	(724,000)	(3,300,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than twelve Months, Unrealized Losses			(96,000)	0
Less than twelve Months, Fair Value			45,628,000	0
Twelve months or more, Unrealized Losses			0	(724,000)
Twelve months or more, Fair Value			0	1,320,000
Unrealized Losses			(96,000)	(724,000)
Fair Value			45,628,000	1,320,000
Investment in Marketable Securities (Textual) [Abstract]
Unrealized gain (loss) on available for sale securities	371,000	(3,566,000)
Impairment loss	$ 2,588,000	$ 35,000