Commitments and Contingencies (Details Textual) - USD ($) $ in Thousands		3 Months Ended		5 Months Ended	9 Months Ended
	Nov. 01, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Commitments and Contingencies (Textual)
Risk of loss or damage, Description					The company paid Ice Floe $53.6 million related to the National Geographic Quest and the vessel was delivered in July of 2017. The Company amended the agreement for the second vessel, the National Geographic Venture, in October 2017. The current contract price is $57.0 million and the vessel is scheduled to be completed in the fourth quarter of 2018, subject to extension for certain events, such as change orders. As of September 30, 2017, the Company has paid Ice Floe, LLC $18.1 million related to the National Geographic Venture. The Company may terminate the applicable Agreement in the event the Builder fails to deliver the vessel within one hundred eighty days of the applicable due date or the Builder becomes insolvent or otherwise bankrupt.
Total of royalty fee and annual gross sales fee		$ 11,676	$ 10,164		$ 31,521	$ 29,294
Insurance revenue		200			$ 1,900
Subsequent Event [Member]
Commitments and Contingencies (Textual)
Percentage of purchase price	20.00%
Nichols Brothers Boat Builders [Member]
Commitments and Contingencies (Textual)
Vessel Construction Agreements, Description					On December 2, 2015, the Company entered into two separate Vessel Construction Agreements, (collectively, the "Agreements") with Ice Floe, LLC, a Washington limited liability company doing business as Nichols Brothers Boat Builders (the "Builder"). The Agreements provide for the Builder to construct two new 236-foot 100-passenger cruise vessels.
National Geographic [Member]
Commitments and Contingencies (Textual)
Balance outstanding		1,900			$ 1,900		$ 1,500
National Geographic [Member] | Royalty Agreement [Member]
Commitments and Contingencies (Textual)
Royalty expense		1,600	1,200		3,900	$ 3,600
World Wildlife Fund [Member] | Royalty Agreement [Member]
Commitments and Contingencies (Textual)
Total of royalty fee and annual gross sales fee		200	$ 200	$ 300	400
National Geographic Venture [Member]
Commitments and Contingencies (Textual)
Cruise vessels at a purchase price		$ 18,100			$ 18,100
Ulstein Verft [Member] | Subsequent Event [Member]
Commitments and Contingencies (Textual)
Vessel Construction Agreements, Description	The Company entered into an agreement with Ulstein Verft to construct a polar ice class vessel with a total purchase price of 1,066.0 million Norwegian Kroner (NOK).
Cruise vessels at a purchase price	$ 134,600