Loans and Leases (Information on How Loans and Leases were Modified as a TDR) (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($) loan	Sep. 30, 2018 USD ($) loan	Sep. 30, 2019 USD ($) loan	Sep. 30, 2018 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	28	37	105	101
Post-Modification Recorded Investment | $	$ 34,249	$ 20,699	$ 76,335	$ 60,083
Commercial Portfolio Segment [Member] | Contractual Interest Rate Reduction [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	1	0	2	0
Post-Modification Recorded Investment | $	$ 12	$ 0	$ 112	$ 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	2	4	8	7
Post-Modification Recorded Investment | $	$ 29	$ 537	$ 222	$ 622
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	3	8	6	10
Post-Modification Recorded Investment | $	$ 225	$ 8,185	$ 296	$ 8,236
Commercial Portfolio Segment [Member] | Commercial and Industrial Sector [Member] | Other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	6	8	25	17
Post-Modification Recorded Investment | $	$ 30,586	$ 10,585	$ 64,642	$ 39,328
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	0	0	2
Post-Modification Recorded Investment | $	$ 0	$ 0	$ 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	0	0	1
Post-Modification Recorded Investment | $	$ 0	$ 0	$ 0	$ 245
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	1	0	3	1
Post-Modification Recorded Investment | $	$ 2,180	$ 0	$ 4,816	$ 5,111
Residential Portfolio Segment [Member] | Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	1	1	5	1
Post-Modification Recorded Investment | $	$ 67	$ 20	$ 1,007	$ 20
Residential Portfolio Segment [Member] | Maturity/Rate Combined [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	1	4	14	7
Post-Modification Recorded Investment | $	$ 368	$ 440	$ 2,216	$ 716
Residential Portfolio Segment [Member] | Other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	2	3	6	16
Post-Modification Recorded Investment | $	$ 243	$ 356	$ 785	$ 2,798
Consumer Portfolio Segment [Member] | Home Equity Loan [Member] | Extended Maturity [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	1	1	5	3
Post-Modification Recorded Investment | $	$ 134	$ 148	$ 504	$ 341
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	3	4	6
Post-Modification Recorded Investment | $	$ 30	$ 170	$ 140	$ 618
Consumer Portfolio Segment [Member] | Home Equity Loan [Member] | Other [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans and Leases | loan	8	5	27	30
Post-Modification Recorded Investment | $	$ 375	$ 258	$ 1,595	$ 1,951