Summary of Significant Accounting Policies (Income Taxes Paid) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Income taxes paid, net	$ 21,000,000	$ 600,000
Proceeds from Income Tax Refunds			$ 830,000