Operating Expenses (Schedule of Selling, General and Administrative Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating Expenses [Abstract]
Employee compensation expenses	$ 44,490	$ 41,729
Buildings, facilities and technology expenses	11,236	10,046
Travel, advertising and promotion expense	5,562	6,081
Professional fees	3,452	3,100
Other SG&A expenses	3,567	2,800
Total selling, general and administrative expenses	$ 68,307	$ 63,756