Summary of Significant Accounting Policies (Summary of Interest Capitalized and Depreciation Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Capitalized interest	$ 137	$ 138	$ 166
Depreciation expense	$ 12,929	$ 14,477	$ 17,869