Loans - Risk Categories of Loans by Class of Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 4,888,139	$ 4,825,214
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	4,768,286	4,694,297
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	60,851	67,296
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	58,708	63,596
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	294	25
Construction and land development
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	379,991	443,568
Construction and land development | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	372,287	428,044
Construction and land development | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,534	10,429
Construction and land development | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	5,170	5,095
Construction and land development | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,190,285	2,132,066
Commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,123,840	2,063,589
Commercial real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	39,942	41,429
Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	26,503	27,048
Commercial real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,400,184	1,324,377
Residential real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,375,087	1,296,634
Residential real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	5,148	3,654
Residential real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	19,949	24,089
Residential real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	0	0
Commercial and financial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	701,747	722,322
Commercial and financial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	684,628	707,663
Commercial and financial | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	10,806	8,387
Commercial and financial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	6,019	6,247
Commercial and financial | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	294	25
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	215,932	202,881
Consumer | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	212,444	198,367
Consumer | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	2,421	3,397
Consumer | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	1,067	1,117
Consumer | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Loans	$ 0	$ 0