Non-performing Loans and Impaired Loans - Payment Status by Class of Loan (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 3,647,450	$ 2,996,548
Total Past Due	16,340	12,605
Loans Not Past Due	26,364	20,334
Total	$ 3,673,814	$ 3,016,771
Total Past Due, Percentage of Total Loans	0.44%	0.42%
Loans Not Past Due, Percentage of Total Loans	0.72%	0.67%
Current,Percentage of total loans	99.28%	99.33%
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 2,054,695	$ 1,715,104
Total Past Due	8,495	6,586
Loans Not Past Due	12,838	10,265
Total	2,067,533	1,725,369
Commercial [Member] | Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	705,186	556,516
Total Past Due	4,083	3,413
Loans Not Past Due	4,411	4,947
Total	709,597	561,463
Commercial [Member] | Non Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	781,012	716,574
Total Past Due	1,251	1,046
Loans Not Past Due	2,080	1,240
Total	783,092	717,814
Commercial [Member] | Residential Spec Homes [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	14,862	4,707
Loans Not Past Due		492
Total	14,862	5,199
Commercial [Member] | Development & Spec Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	40,509	46,479
Total Past Due	140	68
Loans Not Past Due	593	68
Total	41,102	46,547
Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	513,126	390,828
Total Past Due	3,021	2,059
Loans Not Past Due	5,754	3,518
Total	518,880	394,346
Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	947,535	739,650
Total Past Due	4,635	3,269
Loans Not Past Due	7,109	4,636
Total	954,644	744,286
Real Estate [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	791,704	641,500
Total Past Due	4,635	3,269
Loans Not Past Due	7,109	4,636
Total	798,813	646,136
Real Estate [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	22,403	24,030
Total	22,403	24,030
Real Estate [Member] | Mortgage Warehousing [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	133,428	74,120
Total	133,428	74,120
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	645,220	541,794
Total Past Due	3,210	2,750
Loans Not Past Due	6,417	5,433
Total	651,637	547,116
Consumer [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	46,203	38,027
Total Past Due	36	35
Loans Not Past Due	265	146
Total	46,468	38,173
Consumer [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	326,970	311,494
Total Past Due	1,129	916
Loans Not Past Due	2,803	2,683
Total	329,773	314,177
Consumer [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	272,047	192,162
Total Past Due	2,045	1,799
Loans Not Past Due	3,349	2,604
Total	275,396	194,766
30 - 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 8,141	$ 5,100
Total Past Due, Percentage of Total Loans	0.22%	0.17%
30 - 59 Days Past Due [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 3,781	$ 1,719
30 - 59 Days Past Due [Member] | Commercial [Member] | Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	265	537
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	829	175
30 - 59 Days Past Due [Member] | Commercial [Member] | Residential Spec Homes [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		492
30 - 59 Days Past Due [Member] | Commercial [Member] | Development & Spec Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	453
30 - 59 Days Past Due [Member] | Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,234	515
30 - 59 Days Past Due [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,272	1,131
30 - 59 Days Past Due [Member] | Real Estate [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,272	1,131
30 - 59 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,088	2,250
30 - 59 Days Past Due [Member] | Consumer [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	180	93
30 - 59 Days Past Due [Member] | Consumer [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,268	1,396
30 - 59 Days Past Due [Member] | Consumer [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	640	761
60 - 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 1,492	$ 2,061
Total Past Due, Percentage of Total Loans	0.04%	0.07%
60 - 89 Days Past Due [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 499	$ 1,752
60 - 89 Days Past Due [Member] | Commercial [Member] | Owner Occupied Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		997
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		19
60 - 89 Days Past Due [Member] | Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	499	736
60 - 89 Days Past Due [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	125	56
60 - 89 Days Past Due [Member] | Real Estate [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	125	56
60 - 89 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	868	253
60 - 89 Days Past Due [Member] | Consumer [Member] | Direct Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	49	18
60 - 89 Days Past Due [Member] | Consumer [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	250	198
60 - 89 Days Past Due [Member] | Consumer [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	569	37
Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 391	$ 568
Total Past Due, Percentage of Total Loans	0.01%	0.02%
Greater than 90 Days Past Due [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 63	$ 208
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	63
Greater than 90 Days Past Due [Member] | Commercial [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		208
Greater than 90 Days Past Due [Member] | Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	77	180
Greater than 90 Days Past Due [Member] | Real Estate [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	77	180
Greater than 90 Days Past Due [Member] | Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	251	180
Greater than 90 Days Past Due [Member] | Consumer [Member] | Indirect Installment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	156	173
Greater than 90 Days Past Due [Member] | Consumer [Member] | Home Equity Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 95	$ 7