Other Current and Long-Term Assets (Schedule Of Other Current Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Other Assets, Noncurrent [Abstract]
Prepaid expenses	$ 31,997	$ 28,967
Taxes receivable	23,769	35,475
Customer acquisition costs (Notes 2 and 3)	32,768	23,520
Contract assets (Notes 2 and 3)	7,357	0
Deferred sales commissions (Notes 2 and 3)	4,428	0
Other assets (Notes 2 and 3)	12,754	13,178
Other current assets	$ 113,073	$ 101,140