Non-performing Loans and Impaired Loans - Loans by Credit Grades (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Total	$ 2,141,236	$ 2,130,369
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,102,641	1,066,199
Commercial [Member] | Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	339,341	337,548
Commercial [Member] | Non Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	475,766	461,897
Commercial [Member] | Residential Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	6,437	5,006
Commercial [Member] | Development & Spec Land Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	35,395	31,228
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	245,702	230,520
Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	619,948	664,571
Real Estate [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	508,645	508,233
Real Estate [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	21,943	20,611
Real Estate [Member] | Mortgage Warehousing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	89,360	135,727
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	418,647	399,599
Consumer [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	74,195	71,150
Consumer [Member] | Direct Installment Purchased [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	99	119
Consumer [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	166,802	153,204
Consumer [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	177,551	175,126
Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	$ 2,100,127	$ 2,090,978
Percentage of total loans	98.08%	98.15%
Pass [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	$ 1,069,836	$ 1,035,059
Pass [Member] | Commercial [Member] | Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	324,596	322,924
Pass [Member] | Commercial [Member] | Non Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	469,602	455,648
Pass [Member] | Commercial [Member] | Residential Development [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	6,437	5,006
Pass [Member] | Commercial [Member] | Development & Spec Land Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	35,213	31,057
Pass [Member] | Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	233,988	220,424
Pass [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	614,891	659,549
Pass [Member] | Real Estate [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	503,818	503,444
Pass [Member] | Real Estate [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	21,713	20,378
Pass [Member] | Real Estate [Member] | Mortgage Warehousing [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	89,360	135,727
Pass [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	415,400	396,370
Pass [Member] | Consumer [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	73,706	70,638
Pass [Member] | Consumer [Member] | Direct Installment Purchased [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	99	119
Pass [Member] | Consumer [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	166,043	152,496
Pass [Member] | Consumer [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	175,552	173,117
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	$ 9,565	$ 9,029
Percentage of total loans	0.45%	0.42%
Special Mention [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	$ 9,565	$ 9,029
Special Mention [Member] | Commercial [Member] | Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	4,311	4,960
Special Mention [Member] | Commercial [Member] | Non Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	338	341
Special Mention [Member] | Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	4,916	3,728
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	$ 31,544	$ 30,362
Percentage of total loans	1.47%	1.43%
Substandard [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	$ 23,240	$ 22,111
Substandard [Member] | Commercial [Member] | Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	10,434	9,664
Substandard [Member] | Commercial [Member] | Non Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	5,826	5,908
Substandard [Member] | Commercial [Member] | Development & Spec Land Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	182	171
Substandard [Member] | Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	6,798	6,368
Substandard [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	5,057	5,022
Substandard [Member] | Real Estate [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	4,827	4,789
Substandard [Member] | Real Estate [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	230	233
Substandard [Member] | Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	3,247	3,229
Substandard [Member] | Consumer [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	489	512
Substandard [Member] | Consumer [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	759	708
Substandard [Member] | Consumer [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	$ 1,999	$ 2,009
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Percentage of total loans	0.00%	0.00%