Commitments, Contingencies and Concentrations of Credit Risk - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Commitments [Line Items]
Fixed-rate loan commitments	90 days
Rental expense	$ 5.0	$ 5.2	$ 3.2
Minimum
Other Commitments [Line Items]
Interest rates	2.25%
Maximum
Other Commitments [Line Items]
Interest rates	6.75%