Marketable Securities (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Fixed income securities	$ 6,000,000		$ 6,000,000		$ 1,000,000
Payments to acquire marketable securities			18,900,000
Proceeds from sales of marketable securities			13,901,000	$ 6,238,000
Realized losses (gains) from the sale of marketable securities	0	$ 58,000	192,000	(552,000)
Unrealized holding gain on the investments	$ 0	$ 184,000	$ 7,000	$ 653,000
Marketable securities, effective maturity period			1 year 2 months 27 days
Marketable securities, average effective duration			2 months 19 days