Goodwill and Other Intangible Assets - Summary of Goodwill Balances by Component and Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Balance, beginning	$ 254,022	$ 185,223
Business acquisitions	8,154	71,658
Foreign currency translation adjustments	8,375	(2,859)
Balance, ending	270,551	254,022
GES U.S.
Goodwill [Line Items]
Balance, beginning	148,277	112,300
Business acquisitions		35,977
Balance, ending	148,277	148,277
GES International
Goodwill [Line Items]
Balance, beginning	34,460	38,635
Business acquisitions	1,060
Foreign currency translation adjustments	3,320	(4,175)
Balance, ending	38,840	34,460
Pursuit
Goodwill [Line Items]
Balance, beginning	71,285	34,288
Business acquisitions	7,094	35,681
Foreign currency translation adjustments	5,055	1,316
Balance, ending	$ 83,434	$ 71,285