Share-Based Compensation Expense (Schedule Of Share-Based Compensation Expense Showing Amount Attributable To Each Category) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Share-Based Compensation Expense [Abstract]
Amortization of restricted stock unit awards	$ 2,656	$ 2,251
Amortization of stock option awards	219	167
Discount given on employee stock purchase transactions through our Employee Stock Purchase Plan	147	111
Total share-based compensation expense	$ 3,022	$ 2,529