Revenue from Contracts with Customers - Transaction Price Allocated to Future Performance Obligations (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Revenue from Contract with Customer [Abstract]
Contract period	12 months
Remaining performance obligation	$ 26.3
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 16.1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation period	12 months
Marketplaces and Digital Marketing
Revenue from Contract with Customer [Abstract]
Contract period	1 year
Marketplaces and Digital Marketing | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation period	1 year