Taxes (Schedule of Gross Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	$ 7,455	$ 38,877	$ 34,709
Additions based on tax positions related to the current year	3,928	2,979	4,168
Additions for tax positions of prior years	0	2,709
Reductions as a result of lapses in the statute of limitations	0	(37,110)	(37,100)
Ending Balance	$ 11,383	$ 7,455	$ 38,877