Operating expenses (Schedule of Direct Operating Expenses) (Details) - Service Revenue [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Ancillary and logistical service expenses	$ 12,758	$ 13,759
Employee compensation expenses	12,304	10,807
Buildings, facilities and technology expenses	4,039	2,134
Travel, advertising and promotion expenses	6,575	5,868
Other costs of services	3,679	3,501
Total direct expenses	$ 39,355	$ 36,069