Overview and Basis of Presentation - Revenue in Condensed Consolidated Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue:
Total revenue	$ 363,677	$ 364,774	$ 641,105	$ 690,581
Calculated under Revenue Guidance in Effect before Topic 606
Revenue:
Total revenue		364,774		690,581
Exhibition and Event Services [Member] | Calculated under Revenue Guidance in Effect before Topic 606
Revenue:
Total revenue		275,295		551,243
Exhibits and Environments [Member] | Calculated under Revenue Guidance in Effect before Topic 606
Revenue:
Total revenue		44,814		86,737
Pursuit Services [Member] | Calculated under Revenue Guidance in Effect before Topic 606
Revenue:
Total revenue		$ 44,665		$ 52,601