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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	$ 773,478	$ 875,395	$ 763,272	$ 875,219
Interest income recognized, Total	9,552	5,596	20,895	21,405
Interest income recognized, Cash basis	7,430	3,350	14,371	14,421
Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	242,157	228,749	226,243	171,227
Interest income recognized, Total	1,017	611	2,123	1,379
Interest income recognized, Cash basis	1,017	611	2,123	1,379
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	179,327	189,952	161,834	194,337
Interest income recognized, Total	2,327	821	4,433	2,616
Interest income recognized, Cash basis	2,327	821	4,433	2,616
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	53,009	90,493	64,165	94,453
Interest income recognized, Total	81	18	275	131
Interest income recognized, Cash basis	81	18	275	131
Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	17,236	58,500	22,130	74,531
Interest income recognized, Total	1,943	251	2,166	1,694
Interest income recognized, Cash basis	1,943	251	2,166	1,694
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	99,939	104,516	101,997	132,606
Interest income recognized, Total	1,835	1,328	4,639	7,784
Interest income recognized, Cash basis	1,316	776	3,011	6,146
Residential Alt-A [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	116,191	131,574	120,710	135,374
Interest income recognized, Total	1,539	1,643	4,799	5,002
Interest income recognized, Cash basis	618	681	1,962	1,900
Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	21,952	19,268	20,619	17,902
Interest income recognized, Total	231	219	656	540
Interest income recognized, Cash basis	66	81	179	182
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	24,429	33,666	26,521	36,560
Interest income recognized, Total	391	528	1,257	1,742
Interest income recognized, Cash basis	39	67	136	228
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	19,238	18,677	19,053	18,229
Interest income recognized, Total	188	177	547	517
Interest income recognized, Cash basis	$ 23	$ 44	$ 86	$ 145