Summary of Significant Accounting Policies - Goodwil and Income Taxes (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Goodwill
Number of operating segments | item	1
Goodwill impairment	$ 0	$ 0	$ 0
Income Taxes
Uncertain tax positions	$ 0	$ 0