Stock-Based Compensation (Schedule Of Non-Cash Compensation Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total cost of non-cash compensation included in loss before provision for income taxes	$ 38,249	$ 32,915	$ 28,747
Amount charged against loss	38,249	32,915	28,747
Cost of Revenues [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total cost of non-cash compensation included in loss before provision for income taxes	1,013	418	405
Selling, General And Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total cost of non-cash compensation included in loss before provision for income taxes	$ 37,236	$ 32,497	$ 28,342