Concentration of Credit Risk (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2015 USD ($) financial_institution	Dec. 31, 2014 USD ($)	Jun. 30, 2014 USD ($)	Dec. 31, 2013 USD ($)
Risks and Uncertainties [Abstract]
Number of financial institutions with cash deposits held (more than 1) | financial_institution	1
Cash and cash equivalents held at two financial institutions	$ 79,571
Cash and cash equivalents	$ 98,359	$ 93,452	$ 77,406	$ 73,598