Loans and Leases and the Allowance for Credit Losses - Interest Income Recognized on Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	$ 749,774	$ 773,478	$ 778,922	$ 763,272
Interest income recognized, Total	6,961	9,552	23,627	20,895
Interest income recognized, Cash basis	4,235	7,430	16,688	14,371
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	175,256	179,327	177,579	161,834
Interest income recognized, Total	1,806	2,327	3,891	4,433
Interest income recognized, Cash basis	1,806	2,327	3,891	4,433
Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	262,796	242,157	283,783	226,243
Interest income recognized, Total	744	1,017	7,055	2,123
Interest income recognized, Cash basis	744	1,017	7,055	2,123
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	26,996	53,009	30,832	64,165
Interest income recognized, Total	405	81	488	275
Interest income recognized, Cash basis	405	81	488	275
Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	21,500	17,236	19,774	22,130
Interest income recognized, Total	190	1,943	563	2,166
Interest income recognized, Cash basis	190	1,943	563	2,166
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	96,961	99,939	97,229	101,997
Interest income recognized, Total	1,572	1,835	4,778	4,639
Interest income recognized, Cash basis	570	1,316	2,591	3,011
Residential Limited Documentation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	101,877	116,191	104,382	120,710
Interest income recognized, Total	1,501	1,539	4,580	4,799
Interest income recognized, Cash basis	378	618	1,648	1,962
Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	41,740	21,952	33,998	20,619
Interest income recognized, Total	368	231	937	656
Interest income recognized, Cash basis	112	66	295	179
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	18,571	24,429	20,358	26,521
Interest income recognized, Total	303	391	964	1,257
Interest income recognized, Cash basis	19	39	83	136
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	4,077	19,238	10,987	19,053
Interest income recognized, Total	72	188	371	547
Interest income recognized, Cash basis	$ 11	$ 23	$ 74	$ 86