Summary of Significant Accounting Policies (Schedule of Differences Between Book Value and Tax Basis of Net Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Summary of Significant Accounting Policies [Abstract]
Financial statement basis of net assets	$ 4,550	$ 4,114	$ 5,704
Tax basis of net assets (unaudited)	8,336	7,492
Difference	$ (3,786)	$ (3,378)