Summary of Significant Accounting Principles (Accounts Receivable and Allowance for Doubtful Receivables) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Number of days in allowance used n the calculation (greater than)	120 days
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	$ 7,555	$ 0	$ 1,100
Charged to costs and expenses	10,139	8,741	0
Charged to other accounts	0	0	0
Write-offs net of recoveries	4,522	1,186	1,100
Balance at end of year	13,172	$ 7,555	$ 0
Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at end of year	7,500
Other Assets
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at end of year	$ 5,700