Operating Expenses (Schedule of Direct Operating Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Ancillary and logistical service expenses	$ 13,285	$ 11,682	$ 43,516	$ 46,242
Employee compensation expenses	11,555	10,170	37,268	30,120
Buildings, facilities and technology expenses	1,655	1,990	5,961	7,280
Travel, advertising and promotion expenses	5,765	5,921	24,440	20,535
Other costs of services	4,122	3,290	11,534	8,566
Total direct expenses	36,382	33,053	122,719	112,743
Service Revenue [Member]
Total direct expenses	$ 36,382	$ 33,053	$ 122,719	$ 112,743