Fair Value Measurements - Additional Information (Detail) - Fair value, measurements, recurring - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	$ 539,288,000	$ 536,629,000
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	0
Financial liabilities	$ 0	$ 0