Operating expenses (Schedule of Direct Operating Expenses) (Details) - Service Revenue [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Ancillary and logistical service expenses	$ 12,269	$ 12,758
Employee compensation expenses	12,691	12,304
Buildings, facilities and technology expenses	2,701	4,039
Travel, advertising and promotion expenses	4,518	6,575
Other costs of services	3,848	3,679
Total direct expenses	$ 36,027	$ 39,355