Loans and Leases and the Allowance for Credit Losses - Interest Income Recognized on Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	$ 729,652	$ 787,380	$ 743,728	$ 793,497
Interest Income Recognized, Total	5,844	10,894	12,455	16,666
Interest Income Recognized, Cash Basis	3,231	8,628	7,240	12,453
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	200,005	175,028	191,935	178,741
Interest Income Recognized, Total	813	611	1,788	2,085
Interest Income Recognized, Cash Basis	813	611	1,788	2,085
Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	230,767	291,970	251,352	294,277
Interest Income Recognized, Total	805	5,700	1,283	6,311
Interest Income Recognized, Cash Basis	805	5,700	1,283	6,311
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	15,577	31,751	17,552	32,750
Interest Income Recognized, Total	467	41	896	83
Interest Income Recognized, Cash Basis	467	41	896	83
Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	14,213	20,955	14,922	18,911
Interest Income Recognized, Total	86	335	933	373
Interest Income Recognized, Cash Basis	86	335	933	373
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	108,036	97,936	106,166	97,362
Interest Income Recognized, Total	1,465	1,834	3,101	3,206
Interest Income Recognized, Cash Basis	606	1,139	1,380	2,021
Residential Limited Documentation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	95,208	103,795	96,033	105,634
Interest Income Recognized, Total	1,449	1,607	2,949	3,079
Interest Income Recognized, Cash Basis	339	640	723	1,270
Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	46,872	34,234	46,327	30,127
Interest Income Recognized, Total	422	323	821	569
Interest Income Recognized, Cash Basis	91	98	191	183
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	15,506	20,542	15,931	21,252
Interest Income Recognized, Total	262	322	537	661
Interest Income Recognized, Cash Basis	21	28	40	64
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Recorded Investment	3,468	11,169	3,510	14,443
Interest Income Recognized, Total	75	121	147	299
Interest Income Recognized, Cash Basis	$ 3	$ 36	$ 6	$ 63