Loans and Leases and the Allowance for Credit Losses - Interest Income Recognized on Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	$ 799,615	$ 764,080
Interest income recognized, Total	5,772	5,705
Interest income recognized, Cash basis	3,825	3,516
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	182,454	153,070
Interest income recognized, Total	1,474	1,102
Interest income recognized, Cash basis	1,474	1,102
Commercial, Financial, Leasing, etc. [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	296,584	214,618
Interest income recognized, Total	611	604
Interest income recognized, Cash basis	611	604
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	33,750	73,151
Interest income recognized, Total	42	63
Interest income recognized, Cash basis	42	63
Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	16,868	25,540
Interest income recognized, Total	38	55
Interest income recognized, Cash basis	38	55
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	96,788	104,490
Interest income recognized, Total	1,372	1,446
Interest income recognized, Cash basis	882	910
Residential Limited Documentation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	107,473	125,654
Interest income recognized, Total	1,472	1,610
Interest income recognized, Cash basis	630	647
Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	26,019	19,683
Interest income recognized, Total	246	201
Interest income recognized, Cash basis	85	48
Automobile [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	21,962	29,013
Interest income recognized, Total	339	450
Interest income recognized, Cash basis	36	54
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average recorded investment	17,717	18,861
Interest income recognized, Total	178	174
Interest income recognized, Cash basis	$ 27	$ 33