Loans and Allowance for Loan Losses - Past Due Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	$ 3,114,562	$ 1,848,784
Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	92,455	16,058
Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	7,749	8,729
30-89 Days Past Due
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	10,362	5,749
90 Days or More and Accruing Interest
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	1,238	1,329
Financing Receivables Current
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	3,002,758	1,816,919
Commercial and Industrial
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	731,588	386,233
Commercial and Industrial | Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	2,877	478
Commercial and Industrial | Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	469	1,297
Commercial and Industrial | 30-89 Days Past Due
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	388	262
Commercial and Industrial | 90 Days or More and Accruing Interest
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	37	127
Commercial and Industrial | Financing Receivables Current
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	727,817	384,069
Construction
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	435,414	245,905
Construction | Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	8,080	4,319
Construction | Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	239	254
Construction | 30-89 Days Past Due
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	596	441
Construction | 90 Days or More and Accruing Interest
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	44	17
Construction | Financing Receivables Current
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	426,455	240,874
Residential Real Estate | 1-to-4 Family Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	459,467	294,924
Residential Real Estate | 1-to-4 Family Mortgage | Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	24,651	2,107
Residential Real Estate | 1-to-4 Family Mortgage | Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	2,257	2,289
Residential Real Estate | Residential Line of Credit
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	188,392	177,190
Residential Real Estate | Residential Line of Credit | Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	529	601
Residential Real Estate | Multi-Family Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	74,004	44,977
Residential Real Estate | Multi-Family Mortgage | Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	22	28
Residential Real Estate | 30-89 Days Past Due | 1-to-4 Family Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	3,600	3,130
Residential Real Estate | 30-89 Days Past Due | Residential Line of Credit
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	932	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	520	697
Residential Real Estate | 90 Days or More and Accruing Interest | Residential Line of Credit
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	250	433
Residential Real Estate | 90 Days or More and Accruing Interest | Multi-Family Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	87
Residential Real Estate | Financing Receivables Current | 1-to-4 Family Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	428,439	286,701
Residential Real Estate | Financing Receivables Current | Residential Line of Credit
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	186,681	175,017
Residential Real Estate | Financing Receivables Current | Multi-Family Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	73,895	44,949
Commercial Real Estate | Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	473,395	357,346
Commercial Real Estate | Owner Occupied | Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	11,073	3,782
Commercial Real Estate | Owner Occupied | Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	2,308	2,007
Commercial Real Estate | Non-Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	521,416	267,902
Commercial Real Estate | Non-Owner Occupied | Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	18,971	5,340
Commercial Real Estate | Non-Owner Occupied | Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	1,916	2,251
Commercial Real Estate | 30-89 Days Past Due | Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	2,520	186
Commercial Real Estate | 30-89 Days Past Due | Non-Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Loans		158
Commercial Real Estate | 90 Days or More and Accruing Interest | Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	134
Commercial Real Estate | Financing Receivables Current | Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	457,360	351,371
Commercial Real Estate | Financing Receivables Current | Non-Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	500,529	260,153
Consumer and Other
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	230,886	74,307
Consumer and Other | Purchased Credit Impaired
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	26,781	4
Consumer and Other | Non Accruing
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	31	30
Consumer and Other | 30-89 Days Past Due
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	2,326	433
Consumer and Other | 90 Days or More and Accruing Interest
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	166	55
Consumer and Other | Financing Receivables Current
Financing Receivable Recorded Investment Past Due [Line Items]
Loans	$ 201,582	$ 73,785