Loans and Allowance for Loan Losses - Past Due Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	$ 3,166,911	$ 1,848,784
Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	88,835	16,058
Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	8,101	8,729
30-89 Days Past Due
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	15,063	5,749
90 Days or More and Accruing Interest
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	1,996	1,329
Financing Receivables Current
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	3,052,916	1,816,919
Commercial and Industrial
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	715,075	386,233
Commercial and Industrial | Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	2,144	478
Commercial and Industrial | Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	533	1,297
Commercial and Industrial | 30-89 Days Past Due
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	5,859	262
Commercial and Industrial | 90 Days or More and Accruing Interest
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	90	127
Commercial and Industrial | Financing Receivables Current
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	706,449	384,069
Construction
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	448,326	245,905
Construction | Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	7,728	4,319
Construction | Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	300	254
Construction | 30-89 Days Past Due
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	1,412	441
Construction | 90 Days or More and Accruing Interest
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	241	17
Construction | Financing Receivables Current
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	438,645	240,874
Residential Real Estate | 1-to-4 Family Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	480,989	294,924
Residential Real Estate | 1-to-4 Family Mortgage | Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	23,498	2,107
Residential Real Estate | 1-to-4 Family Mortgage | Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	2,548	2,289
Residential Real Estate | Residential Line of Credit
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	194,986	177,190
Residential Real Estate | Residential Line of Credit | Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	699	601
Residential Real Estate | Multi-Family Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	62,374	44,977
Residential Real Estate | Multi-Family Mortgage | Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	20	28
Residential Real Estate | 30-89 Days Past Due | 1-to-4 Family Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	4,678	3,130
Residential Real Estate | 30-89 Days Past Due | Residential Line of Credit
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	527	1,139
Residential Real Estate | 90 Days or More and Accruing Interest | 1-to-4 Family Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	956	697
Residential Real Estate | 90 Days or More and Accruing Interest | Residential Line of Credit
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	134	433
Residential Real Estate | Financing Receivables Current | 1-to-4 Family Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	449,309	286,701
Residential Real Estate | Financing Receivables Current | Residential Line of Credit
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	193,626	175,017
Residential Real Estate | Financing Receivables Current | Multi-Family Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	62,354	44,949
Commercial Real Estate | Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	495,872	357,346
Commercial Real Estate | Owner Occupied | Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	11,962	3,782
Commercial Real Estate | Owner Occupied | Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	2,582	2,007
Commercial Real Estate | Non-Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	551,588	267,902
Commercial Real Estate | Non-Owner Occupied | Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	18,164	5,340
Commercial Real Estate | Non-Owner Occupied | Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	1,371	2,251
Commercial Real Estate | 30-89 Days Past Due | Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	521	186
Commercial Real Estate | 30-89 Days Past Due | Non-Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	121	158
Commercial Real Estate | 90 Days or More and Accruing Interest | Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	358
Commercial Real Estate | Financing Receivables Current | Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	480,449	351,371
Commercial Real Estate | Financing Receivables Current | Non-Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	531,932	260,153
Consumer and Other
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	217,701	74,307
Consumer and Other | Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	25,319	4
Consumer and Other | Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	68	30
Consumer and Other | 30-89 Days Past Due
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	1,945	433
Consumer and Other | 90 Days or More and Accruing Interest
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	217	55
Consumer and Other | Financing Receivables Current
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	$ 190,152	$ 73,785