Restructuring Charges - Changes to Restructuring Liability by Major Restructuring Activity (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Restructuring Cost And Reserve [Line Items]
Beginning balance		$ 3,439	$ 3,435	$ 5,230
Restructuring charges		1,174	3,059	6,066
Cash payments		(1,643)	(1,934)	(5,899)
Non-cash items	[1]		(1,167)	(1,906)
Adjustment to liability		42	46	(56)
Ending balance		3,012	3,439	3,435
GES | Severance & Employee Benefits
Restructuring Cost And Reserve [Line Items]
Beginning balance		1,609	1,976	2,440
Restructuring charges		648	624	1,829
Cash payments		(623)	(988)	(2,302)
Non-cash items	[1]		0	0
Adjustment to liability		0	(3)	9
Ending balance		1,634	1,609	1,976
GES | Facilities
Restructuring Cost And Reserve [Line Items]
Beginning balance		1,818	1,433	2,766
Restructuring charges		327	2,351	4,107
Cash payments		(807)	(863)	(3,506)
Non-cash items	[1]		(1,167)	(1,906)
Adjustment to liability		40	64	(28)
Ending balance		1,378	1,818	1,433
Other Restructuring | Severance & Employee Benefits
Restructuring Cost And Reserve [Line Items]
Beginning balance		12	26	24
Restructuring charges		199	84	130
Cash payments		(213)	(83)	(91)
Non-cash items	[1]		0	0
Adjustment to liability		2	(15)	(37)
Ending balance		$ 0	$ 12	$ 26

[1] Represents non-cash adjustments related to a write-down of certain ROU assets and leasehold improvements as a result of vacating certain facilities prior to the lease term during the year ended December 31, 2022 and a write down of certain ROU assets as a result of vacating certain facilities prior to the lease term during the year ended December 31, 2021.