Operating Expenses (Schedule Of Selling, General And Administrative Expenses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Expenses [Abstract]
Employee compensation expenses	$ 166,418	$ 159,398	$ 158,448
Building and facilities expenses	41,404	41,725	40,820
Travel, advertising and promotion expense	22,307	22,454	20,728
Other SG&A expenses	24,861	24,643	23,740
Total selling, general and administrative expenses	$ 254,990	$ 248,220	$ 243,736