Loans and Leases - Schedule of Modified TDRs (Detail) - TDRs Occurring during the Period - TDRs - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Modifications
TDRs during period on accrual status			$ 20,200	$ 40,500
TDRs during period on non-accrual status			25,800	11,000
Extended maturities	$ 3,658	$ 3,184	10,020	18,177
Maturity and interest rate adjustment	267	204	368	5,151
Movement to or extension of interest-rate only payments	0	3,560	48	3,692
Interest rate adjustment	0	0	101	25
Financing Receivable Modifications Forbearance	802	841	14,386	5,528
Other concession(s)	1,810	16,797	21,031	18,944
TDRs during period	6,537	24,586	45,954	51,517
Commercial Loans | Commercial real estate - Construction
Financing Receivable, Modifications
TDRs during period	0	1,164	976	1,164
Commercial Loans | Commercial real estate - owner-occupied
Financing Receivable, Modifications
TDRs during period	2,312	713	13,373	2,411
Commercial Loans | Commercial real estate - non-owner-occupied
Financing Receivable, Modifications
TDRs during period	1,790	5,298	3,064	11,505
Commercial Loans | Commercial and industrial
Financing Receivable, Modifications
TDRs during period	804	12,502	22,769	19,399
Residential Mortgage | Residential mortgage
Financing Receivable, Modifications
TDRs during period	255	392	837	1,030
Consumer and Other Loans | Consumer - Home equity
Financing Receivable, Modifications
TDRs during period	1,124	3,479	4,047	13,471
Consumer and Other Loans | Consumer - Other
Financing Receivable, Modifications
TDRs during period	$ 252	$ 1,038	$ 888	$ 2,537