Note 3 - Revenues - Disaggregation of Revenues by Type (Details)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Tour Revenues	100.00%	100.00%
Guest Ticket [Member]
Tour Revenues	88.00%	90.00%
Guest Ticket [Member] | Sales Channel, Directly to Consumer [Member]
Tour Revenues	41.00%	41.00%
Guest Ticket [Member] | Sales Channel, National Geographic [Member]
Tour Revenues	18.00%	19.00%
Guest Ticket [Member] | Sales Channel, Agencies [Member]
Tour Revenues	24.00%	24.00%
Guest Ticket [Member] | Sales Channel, Affinity [Member]
Tour Revenues	5.00%	6.00%
Other Tour [Member]
Tour Revenues	12.00%	10.00%