Cash Equivalents, Restricted Cash and Investments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($) Investment	Dec. 31, 2018 USD ($)
Cash And Cash Equivalents [Abstract]
Maturity period available-for-sale securities	less than two years
Significant realized gains or losses on available-for-sale securities	$ 0
Cash	$ 8,900,000	$ 2,100,000
Number of available-for-sale securities in a continuous unrealized loss position for more than 12 months | Investment	0
Number of available-for-sale securities in a continuous unrealized loss position for more than 12 months	$ 0