Cash, Cash Equivalents and Marketable Securities (Details) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Cash, Cash Equivalents and Marketable Securities
Cash and cash equivalents	$ 1,200,000	$ 1,200,000	$ 18,130,000	$ 8,312,000	$ 12,416,000
Available-for-sale securities	49,999,000	49,999,000	50,027,000
Net realized gains or losses	$ 0	$ 0