Summary of Significant Accounting Policies (Accounts Receivable and Allowance for Doubtful Receivables) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Number of days in allowance used n the calculation (greater than)	120 days
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of year	$ 0	$ 1,100	$ 244
Charged to costs and expenses	8,741	0	1,100
Charged to other accounts	0	0	0
Write-offs net of recoveries	1,186	1,100	244
Balance at end of year	$ 7,555	$ 0	$ 1,100