Concentration of Credit Risk (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2017 USD ($) financial_institution	Dec. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Risks and Uncertainties [Abstract]
Number of financial institutions with cash deposits held (more than 1) | financial_institution	1
Cash and cash equivalents held at one financial institutions	$ 44,584
Cash and cash equivalents	$ 67,392	$ 45,596	$ 58,929	$ 76,217