Loans and Leases - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($) Property	Dec. 31, 2018 USD ($) Property
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable	$ 11,742,000	$ 13,331,000
Loans and leases receivable pledged to secure advances	1,350,000,000	1,100,000,000
Loans 90 days or more past due and still accruing	$ 0	$ 4,000
Number of real estate properties | Property	2	7
Other real estate owned ("OREO")	$ 63,000	$ 663,000
TDR loans receivable	$ 56,300,000	10,300,000
Principal and interest due	6 months
Reserves relating to loans included in allowance for loan and lease losses	$ 22,700,000	300,000
Loans default payment past due period	30 days
Total recorded investment	$ 132,000	132,000
Loans and lease receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable	$ 10,000,000.0	$ 10,900,000