Financial Instruments (Available-for-sale Debt Securities) - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Corporate and municipal bonds	$ 29,400	$ 58,900
Maturity dates of bonds, start date	2020-10
Maturity dates of bonds, end date	2024-11
Unrealized losses on securities	$ 100
Funds held for clients	$ 123,755	179,502
Certified Deposits and Other Depository Assets [Member]
Schedule Of Available For Sale Securities [Line Items]
Funds held for clients		$ 2,500