Revenue and Related Contract Costs and Contract Liabilities - Narrative (Details)	9 Months Ended
	Sep. 30, 2018 USD ($)
Disaggregation Of Revenue [Line Items]
Revenue recognition description of capitalized contract costs	Capitalized contract costs are expensed upon the transfer of the related goods or services and are included in cost of services or cost of products, as applicable
Capitalized contract costs to obtain contracts	$ 1,800,000
Capitalized contract costs to fulfill contracts	27,400,000
Impairment loss on capitalized contract costs	$ 0
Maximum
Disaggregation Of Revenue [Line Items]
Unsatisfied performance obligations period	1 year
GES
Disaggregation Of Revenue [Line Items]
Performance obligation description of payment terms	Payment terms are generally within 30-60 days and contain no significant financing components
GES | Minimum
Disaggregation Of Revenue [Line Items]
Performance obligation payment terms	30 days
GES | Maximum
Disaggregation Of Revenue [Line Items]
Performance obligation payment terms	60 days
Pursuit
Disaggregation Of Revenue [Line Items]
Performance obligation description of payment terms	When credit is extended, payment terms are generally within 30 days and contain no significant financing components
Performance obligation payment terms	30 days