Loans - Risk Profile Based Upon Payment Activity (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing	$ 5,837	$ 6,922
Recorded investment	1,961,543	1,042,241
Total Loans	1,969,660	1,049,698	$ 966,545
Commercial real estate - owner occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing	0	0
Recorded investment	442,236	250,440
Total Loans	443,128	250,440	238,224
Commercial real estate - nonowner occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing	0	0
Recorded investment	435,181	184,688
Total Loans	435,181	184,688	174,342
Real estate construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing	26	940
Recorded investment	104,167	90,882
Total Loans	104,193	91,822	79,621
Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing	572	431
Recorded investment	511,212	203,885
Total Loans	512,621	204,413	202,605
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing	5,236	5,551
Recorded investment	443,705	305,497
Total Loans	449,450	311,486	264,794
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing	3	0
Recorded investment	25,042	6,849
Total Loans	25,087	6,849	$ 6,959
Non-performing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing	5,837	6,922
Non-performing | Commercial real estate - owner occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing	0	0
Non-performing | Commercial real estate - nonowner occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing	0	0
Non-performing | Real estate construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing	26	940
Non-performing | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing	572	431
Non-performing | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing	5,236	5,551
Non-performing | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-performing	3	0
Performing
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment	1,963,823	1,042,776
Performing | Commercial real estate - owner occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment	443,128	250,440
Performing | Commercial real estate - nonowner occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment	435,181	184,688
Performing | Real estate construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment	104,167	90,882
Performing | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment	512,049	203,982
Performing | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment	444,214	305,935
Performing | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment	$ 25,084	$ 6,849