Securities - Schedule of Federal Reserve Bank Stock and Federal Home Loan Bank Stock and Other Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule of Other Securities [Line Items]
Fair Value	$ 154,206	$ 108,420
Federal Reserve Bank Stock and Other Securities [Member]
Schedule of Other Securities [Line Items]
Amortized Cost	151,146	103,130
Gross Unrealized Gains	3,270	5,295
Gross Unrealized Losses	(210)	(5)
Fair Value	154,206	108,420
FRB and FHLB stock [Member] | Federal Reserve Bank Stock and Other Securities [Member]
Schedule of Other Securities [Line Items]
Amortized Cost	33,252	33,262
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	33,252	33,262
Other securities - non-marketable [Member] | Federal Reserve Bank Stock and Other Securities [Member]
Schedule of Other Securities [Line Items]
Amortized Cost	117,894	69,868
Gross Unrealized Gains	3,270	5,295
Gross Unrealized Losses	(210)	(5)
Fair Value	$ 120,954	$ 75,158