Securities - Schedule of Other Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule of Other Securities [Line Items]
Other securities	$ 296,053	$ 108,420
FRB and FHLB stock [Member]
Schedule of Other Securities [Line Items]
Other securities	33,222	33,262
Equity Securities With Readily Determinable Fair Values [Member]
Schedule of Other Securities [Line Items]
Other securities	134,197
Equity Securities Without Readily Determinable Fair Values [Member]
Schedule of Other Securities [Line Items]
Other securities	$ 128,634	$ 75,158