Cash Equivalents and Short Term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 28,486	$ 46,582	$ 44,078	$ 6,754
Short term investments	3,000	5,750
Certificates of Deposit
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents		1,250
Short term investments	$ 3,000	$ 5,750