Operating Expenses (Schedule of Direct Operating Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Ancillary and logistical service expenses	$ 13,759	$ 14,580
Employee compensation expenses	10,807	9,019
Buildings, facilities and technology expenses	2,134	2,627
Travel, advertising and promotion expenses	5,868	6,808
Other costs of services	3,501	3,623
Total direct expenses	36,069	36,657
Service Revenues [Member]
Total direct expenses	$ 36,069	$ 36,657