Other Current and Noncurrent Assets (Schedule Of Other Current Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Current and Noncurrent Assets [Abstract]
Prepaid expenses	$ 28,967	$ 25,746
Taxes receivable	35,475	27,672
Customer acquisition costs, net	23,520	18,085
Other assets	13,178	19,703
Total other current assets	$ 101,140	$ 91,206