Overview and Basis of Presentation - Revenue in Condensed Consolidated Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue:
Total revenue	$ 277,428	$ 325,807
Calculated under Revenue Guidance in Effect before Topic 606
Revenue:
Total revenue		325,807
Exhibition and Event Services [Member] | Calculated under Revenue Guidance in Effect before Topic 606
Revenue:
Total revenue		275,948
Exhibits and Environments [Member] | Calculated under Revenue Guidance in Effect before Topic 606
Revenue:
Total revenue		41,923
Pursuit Services [Member] | Calculated under Revenue Guidance in Effect before Topic 606
Revenue:
Total revenue		$ 7,936