Quarterly report pursuant to Section 13 or 15(d)

Loans and Leases - Additional Information (Detail)

v3.10.0.1
Loans and Leases - Additional Information (Detail) - USD ($)
 9 Months Ended
Sep. 30, 2018
Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Total gross loans and leases receivable $ 4,582,883,000 $ 4,304,458,000
Accrued interest receivable 13,646,000 12,770,000
Loans and leases receivable 1,100,000,000 1,100,000,000
Loans 90 days or more past due and still accruing 0 0
Commitments to lend additional funds to borrowers whose loans are impaired 0 0
Non-accrual Non-PCI loans and leases 18,283,000 15,805,000
Other real estate owned (OREO), net 877,000 1,946,000
TDR loans receivable $ 13,400,000 15,400,000
Principal and interest due 3 months  
Reserves relating to loans included in allowance for loan losses $ 2,800,000 2,200,000
Home equity line of credit [Member]    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Total gross loans and leases receivable 10,900,000 14,200,000
Loans and Finance Receivables [Member]    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Accrued interest receivable 11,200,000 10,200,000
Non-Accrual Loans and Leases, Excluding PCI Loans [Member]    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Non-accrual Non-PCI loans and leases $ 1,600,000 $ 900,000