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, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	$ 787,380	$ 752,253	$ 793,497	$ 758,167
Interest income recognized, Total	10,894	5,638	16,666	11,343
Interest income recognized, Cash basis	8,628	3,425	12,453	6,941
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	175,028	153,105	178,741	153,088
Interest income recognized, Total	611	1,004	2,085	2,106
Interest income recognized, Cash basis	611	1,004	2,085	2,106
Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	291,970	221,952	294,277	218,285
Interest income recognized, Total	5,700	502	6,311	1,106
Interest income recognized, Cash basis	5,700	502	6,311	1,106
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	31,751	66,334	32,750	69,742
Interest income recognized, Total	41	131	83	194
Interest income recognized, Cash basis	41	131	83	194
Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	20,955	23,614	18,911	24,577
Interest income recognized, Total	335	168	373	223
Interest income recognized, Cash basis	335	168	373	223
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	97,936	101,560	97,362	103,025
Interest income recognized, Total	1,834	1,358	3,206	2,804
Interest income recognized, Cash basis	1,139	785	2,021	1,695
Residential Limited Documentation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	103,795	120,286	105,634	122,970
Interest income recognized, Total	1,607	1,650	3,079	3,260
Interest income recognized, Cash basis	640	697	1,270	1,344
Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	34,234	20,221	30,127	19,952
Interest income recognized, Total	323	224	569	425
Interest income recognized, Cash basis	98	65	183	113
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	20,542	26,123	21,252	27,568
Interest income recognized, Total	322	416	661	866
Interest income recognized, Cash basis	28	43	64	97
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	11,169	19,058	14,443	18,960
Interest income recognized, Total	121	185	299	359
Interest income recognized, Cash basis	$ 36	$ 30	$ 63	$ 63