Other Current Assets - Schedule of Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Income tax receivable	$ 6,809	$ 4,237
Prepaid vendor payments	6,225	5,048
Prepaid software maintenance	4,350	3,386
Prepaid insurance	3,708	2,610
Prepaid taxes	819	912
Prepaid rent	791	730
Prepaid other	2,858	2,172
Other	147	646
Other current assets	$ 25,707	$ 19,741	[1]

[1] Contract costs primarily consist of deferred core services costs (including labor and vendor purchases) required to service future exhibitions, conferences and other events, and commission expenses incurred to obtain contracts. All such costs were previously included in “Inventories” and in certain other assets. As a result of the changes noted above, deferred core services costs related to exhibitions and events that are scheduled to occur longer than one year in the future are currently included in “Other investments and assets”. The impact of this change reduced total current assets at December 31, 2017 by $0.7 million. The amount of deferred core services costs included in “Other investments and assets” at September 30, 2018 was $4.4 million.