Loans and Leases (Information on How Loans and Leases were Modified as a TDR) (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) loan	Jun. 30, 2018 USD ($) loan	Jun. 30, 2019 USD ($) loan	Jun. 30, 2018 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	34	38	77	64
Post-Modification Recorded Investment | $	$ 15,144	$ 32,729	$ 42,086	$ 39,384
Residential Portfolio Segment [Member] | Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	3	0	4	0
Post-Modification Recorded Investment | $	$ 421	$ 0	$ 940	$ 0
Residential Portfolio Segment [Member] | Maturity/Rate Combined [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	8	3	13	3
Post-Modification Recorded Investment | $	$ 1,397	$ 276	$ 1,848	$ 276
Residential Portfolio Segment [Member] | Other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	2	8	4	13
Post-Modification Recorded Investment | $	$ 281	$ 1,685	$ 542	$ 2,442
Consumer Portfolio Segment [Member] | Home Equity Loan [Member] | Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	2	0	4	2
Post-Modification Recorded Investment | $	$ 225	$ 0	$ 370	$ 193
Consumer Portfolio Segment [Member] | Home Equity Loan [Member] | Maturity/Rate Combined [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	2	1	2	3
Post-Modification Recorded Investment | $	$ 110	$ 335	$ 110	$ 448
Consumer Portfolio Segment [Member] | Home Equity Loan [Member] | Other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	6	14	19	25
Post-Modification Recorded Investment | $	$ 466	$ 915	$ 1,220	$ 1,693
Commercial Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	1	0	1	0
Post-Modification Recorded Investment | $	$ 100	$ 0	$ 100	$ 0
Commercial Portfolio Segment [Member] | Commercial and Industrial Sector [Member] | Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	4	0	6	3
Post-Modification Recorded Investment | $	$ 69	$ 0	$ 193	$ 85
Commercial Portfolio Segment [Member] | Commercial and Industrial Sector [Member] | Maturity/Rate Combined [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	2	2	3	2
Post-Modification Recorded Investment | $	$ 46	$ 51	$ 71	$ 51
Commercial Portfolio Segment [Member] | Commercial and Industrial Sector [Member] | Other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	4	7	19	9
Post-Modification Recorded Investment | $	$ 12,029	$ 24,059	$ 34,056	$ 28,743
Commercial Real Estate Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	0	1	0	1
Post-Modification Recorded Investment | $	$ 0	$ 245	$ 0	$ 245
Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member] | Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	0	1	0	2
Post-Modification Recorded Investment | $	$ 0	$ 52	$ 0	$ 97
Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member] | Maturity/Rate Combined [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	0	1	0	1
Post-Modification Recorded Investment | $	$ 0	$ 5,111	$ 0	$ 5,111
Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member] | Other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	0	0	2	0
Post-Modification Recorded Investment | $	$ 0	$ 0	$ 2,636	$ 0