Fair Value Measurements - Summary of Company's Fair Value Hierarchy for its Financial Assets and Liabilities (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Assets:
Fair value of investments	$ 5,367	$ 255
Liabilities
Fair value of liabilities	(2,443)	(4,196)
Contingent Purchase Price [Member]
Liabilities
Fair value of liabilities	(2,443)	(4,196)
Money Market Funds [Member]
Assets:
Fair value of cash equivalents	5,367	255
Level 1 [Member]
Assets:
Fair value of investments	5,367	255
Level 1 [Member] | Money Market Funds [Member]
Assets:
Fair value of cash equivalents	5,367	255
Level 3 [Member]
Liabilities
Fair value of liabilities	(2,443)	(4,196)
Level 3 [Member] | Contingent Purchase Price [Member]
Liabilities
Fair value of liabilities	$ (2,443)	$ (4,196)