Loans and Leases - Schedule of Modified TDRs (Detail) - Troubled Debt Restructurings [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Financing Receivable, Modifications
TDRs during period on accrual status			$ 20,600	$ 22,800
TDRs during period on non-accrual status			26,100	5,600
Extended maturities	$ 1,790	$ 8,488	7,193	15,014
Maturity and interest rate adjustment	0	3,886	102	6,502
Movement to or extension of interest-rate only payments	1,316	38	1,364	138
Interest rate adjustment	0	26	103	26
Financing Receivable Modifications Forbearance	1,405	3,466	13,936	4,687
Other concession(s)	15,597	1,988	23,993	2,031
TDRs during period	$ 20,108	$ 17,892	$ 46,691	$ 28,398