Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument Fair Value Carrying Value [Line Items]
Transfers among the Level 1, Level 2 and Level 3 categories	$ 0	$ 0
Marketable securities fair value held to maturity	137,100,000	5,900,000
Impairment of assets	$ 0	$ 0
Maximum [Member]
Debt Instrument Fair Value Carrying Value [Line Items]
Marketable securities, remaining contractual maturities	1 year	1 year
Marketable securities held, matuirity period	2 years
Minimum [Member]
Debt Instrument Fair Value Carrying Value [Line Items]
Marketable securities held, matuirity period	1 year