Operating Expenses (Schedule of Selling, General and Administrative Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Operating Expenses [Abstract]
Employee compensation expenses	$ 43,077	$ 36,287	$ 135,129	$ 122,062
Buildings, facilities and technology expenses	12,466	10,516	36,671	30,849
Travel, advertising and promotion expense	6,273	5,388	18,594	16,274
Professional fees	3,675	3,157	9,524	9,456
Other SG&A expenses	3,509	2,822	11,235	8,524
Total selling, general and administrative expenses	$ 69,000	$ 58,170	$ 211,153	$ 187,165