Subsequent Event - Additional Information (Detail) - Subsequent Event $ / shares in Units, $ in Millions	Jan. 01, 2020 USD ($) branch loan_office $ / shares shares
Subsequent Event [Line Items]
Share price (in dollars per share) | $ / shares	$ 25.54
Purchase accounting adjustments, assets	$ 10,200
Purchase accounting adjustments, loans	7,800
Purchase accounting adjustments, deposits	7,900
Two River Bancorp
Subsequent Event [Line Items]
Consideration paid	$ 197
Stock issued during period, shares, acquisitions | shares	5,818,687
Number of branches (branches) | branch	14
Number of loan production offices (loan office) | loan_office	1
Purchase accounting adjustments, assets	$ 1,100
Purchase accounting adjustments, loans	938
Purchase accounting adjustments, deposits	942
Country Bank Holding Company, Inc
Subsequent Event [Line Items]
Consideration paid	$ 113
Stock issued during period, shares, acquisitions | shares	4,418,000
Number of branches (branches) | branch	5
Number of loan production offices (loan office) | loan_office	1
Purchase accounting adjustments, assets	$ 798
Purchase accounting adjustments, loans	616
Purchase accounting adjustments, deposits	$ 654