Note Allowance for loan losses (Troubled debt restructurings loan count by type of modification) (Detail) - loans	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Troubled Debt Restructuring
Reduction In Interest Rate	286	323
Extension of Maturity Date	64	54
Combination Interest Rate Reduction Maturity Date Extension	162	42
Other Modifications	66	173
CRE non-owner occupied
Troubled Debt Restructuring
Reduction In Interest Rate	0	2
Extension of Maturity Date	1	5
Combination Interest Rate Reduction Maturity Date Extension	0	0
Other Modifications	0	0
CRE owner occupied
Troubled Debt Restructuring
Reduction In Interest Rate	0	0
Extension of Maturity Date	10	19
Combination Interest Rate Reduction Maturity Date Extension	0	0
Other Modifications	0	0
Commercial and industrial
Troubled Debt Restructuring
Reduction In Interest Rate	0	3
Extension of Maturity Date	16	19
Combination Interest Rate Reduction Maturity Date Extension	0	0
Other Modifications	0	0
Construction
Troubled Debt Restructuring
Reduction In Interest Rate		1
Extension of Maturity Date		0
Combination Interest Rate Reduction Maturity Date Extension		0
Other Modifications		0
Mortgages
Troubled Debt Restructuring
Reduction In Interest Rate	6	19
Extension of Maturity Date	27	4
Combination Interest Rate Reduction Maturity Date Extension	157	36
Other Modifications	0	23
Credit cards
Troubled Debt Restructuring
Reduction In Interest Rate	122	131
Extension of Maturity Date	0	0
Combination Interest Rate Reduction Maturity Date Extension	1	0
Other Modifications	66	150
Home equity lines of credit
Troubled Debt Restructuring
Reduction In Interest Rate	0	0
Extension of Maturity Date	6	5
Combination Interest Rate Reduction Maturity Date Extension	4	4
Other Modifications	0	0
Personal Loan
Troubled Debt Restructuring
Reduction In Interest Rate	152	160
Extension of Maturity Date	2	2
Combination Interest Rate Reduction Maturity Date Extension	0	0
Other Modifications	0	0
Auto Loan
Troubled Debt Restructuring
Reduction In Interest Rate	0	0
Extension of Maturity Date	2	0
Combination Interest Rate Reduction Maturity Date Extension	0	1
Other Modifications	0	0
Other
Troubled Debt Restructuring
Reduction In Interest Rate	6	7
Extension of Maturity Date	0	0
Combination Interest Rate Reduction Maturity Date Extension	0	1
Other Modifications	0	0