Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value Measurements, Inter-transfers between Levels	$ 0	$ 0
Net changes in the fair value of contingent consideration	2,617,000	(1,494,000)	$ (994,000)
Other Expense
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Net changes in the fair value of contingent consideration	$ 2,600,000
Other Income
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Net changes in the fair value of contingent consideration		$ (1,500,000)	$ (1,000,000)