Fair Value Measurements - Summary of Changes in Fair Value of Company's Level 3 Assets and Liabilities (Parenthetical) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Level 3 Assets [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis Unobservable Input Reconciliation [Line Items]
Net unrealized gains (losses)	$ (117)	$ (781)	$ 61
Contingent Consideration Liability [Member]
Fair Value of Assets and Liabilities Measured on Recurring Basis Unobservable Input Reconciliation [Line Items]
Net unrealized (gains) losses		$ 17,170	$ (18,932)