Investments - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Long-term GICs
Schedule of Investments [Line Items]
Commercial paper	$ 75,260,000	$ 0
Securities	$ 718,000	$ 0
Minimum | Short-term GICs
Schedule of Investments [Line Items]
Investments interest rate	0.80%
Minimum | Long-term GICs
Schedule of Investments [Line Items]
Investments interest rate	0.90%
Long-term investments maturity term	12 months
Maximum | Short-term GICs
Schedule of Investments [Line Items]
Investments interest rate	2.00%
Short-term investments maturity term	12 months
Maximum | Long-term GICs
Schedule of Investments [Line Items]
Investments interest rate	1.00%
Long-term investments maturity term	24 months