Operating expenses (Schedule of Direct Operating Expenses) (Details) - Service Revenues [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Ancillary and logistical service expenses	$ 13,446	$ 14,819	$ 24,201	$ 27,088
Employee compensation expenses	17,045	14,953	32,966	29,483
Buildings, facilities and technology expenses	3,025	2,304	6,879	5,005
Travel, advertising and promotion expenses	7,200	5,299	12,372	9,817
Other costs of services	4,323	3,926	7,636	7,774
Total direct expenses	$ 45,039	$ 41,301	$ 84,054	$ 79,167