Non-performing Loans and Impaired Loans - Payment Status by Class of Loan (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 5,737	$ 6,556
Loans Not Past Due	2,135,499	2,123,813
Total	$ 2,141,236	$ 2,130,369
Total Past Due, Percentage of Total Loans	0.27%	0.31%
Loans Not Past Due, Percentage of Total Loans	99.73%	99.69%
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 2,846	$ 2,591
Loans Not Past Due	1,099,795	1,063,608
Total	1,102,641	1,066,199
Commercial [Member] | Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,523	1,251
Loans Not Past Due	337,818	336,297
Total	339,341	337,548
Commercial [Member] | Non Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	195	357
Loans Not Past Due	475,571	461,540
Total	475,766	461,897
Commercial [Member] | Residential Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	478
Loans Not Past Due	5,959	5,006
Total	6,437	5,006
Commercial [Member] | Development & Spec Land Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	85	1
Loans Not Past Due	35,310	31,227
Total	35,395	31,228
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	565	982
Loans Not Past Due	245,137	229,538
Total	245,702	230,520
Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,502	1,009
Loans Not Past Due	618,446	663,562
Total	619,948	664,571
Real Estate [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,319	1,009
Loans Not Past Due	507,326	507,224
Total	508,645	508,233
Real Estate [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	183
Loans Not Past Due	21,760	20,611
Total	21,943	20,611
Real Estate [Member] | Mortgage Warehousing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans Not Past Due	89,360	135,727
Total	89,360	135,727
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,389	2,956
Loans Not Past Due	417,258	396,643
Total	418,647	399,599
Consumer [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	28	143
Loans Not Past Due	74,167	71,007
Total	74,195	71,150
Consumer [Member] | Direct Installment Purchased [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans Not Past Due	99	119
Total	99	119
Consumer [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	969	1,625
Loans Not Past Due	165,833	151,579
Total	166,802	153,204
Consumer [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	392	1,188
Loans Not Past Due	177,159	173,938
Total	177,551	175,126
30 - 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 4,918	$ 5,684
Total Past Due, Percentage of Total Loans	0.23%	0.27%
30 - 59 Days Past Due [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 2,604	$ 2,408
30 - 59 Days Past Due [Member] | Commercial [Member] | Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,523	1,068
30 - 59 Days Past Due [Member] | Commercial [Member] | Non Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	103	357
30 - 59 Days Past Due [Member] | Commercial [Member] | Residential Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	478
30 - 59 Days Past Due [Member] | Commercial [Member] | Development & Spec Land Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	85	1
30 - 59 Days Past Due [Member] | Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	415	982
30 - 59 Days Past Due [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,255	886
30 - 59 Days Past Due [Member] | Real Estate [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,072	886
30 - 59 Days Past Due [Member] | Real Estate [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	183
30 - 59 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,059	2,390
30 - 59 Days Past Due [Member] | Consumer [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	26	139
30 - 59 Days Past Due [Member] | Consumer [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	707	1,339
30 - 59 Days Past Due [Member] | Consumer [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	326	912
60 - 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 574	$ 631
Total Past Due, Percentage of Total Loans	0.03%	0.03%
60 - 89 Days Past Due [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 92
60 - 89 Days Past Due [Member] | Commercial [Member] | Non Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	92
60 - 89 Days Past Due [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	247	$ 123
60 - 89 Days Past Due [Member] | Real Estate [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	247	123
60 - 89 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	235	508
60 - 89 Days Past Due [Member] | Consumer [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2	4
60 - 89 Days Past Due [Member] | Consumer [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	193	237
60 - 89 Days Past Due [Member] | Consumer [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	40	267
Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 245	$ 241
Total Past Due, Percentage of Total Loans	0.01%	0.01%
Greater than 90 Days Past Due [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 150	$ 183
Greater than 90 Days Past Due [Member] | Commercial [Member] | Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		183
Greater than 90 Days Past Due [Member] | Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	150
Greater than 90 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	95	58
Greater than 90 Days Past Due [Member] | Consumer [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	69	49
Greater than 90 Days Past Due [Member] | Consumer [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 26	$ 9