Loans and Allowance for Loan Losses - Loans Outstanding by Major Lending Classification (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable Recorded Investment Past Due [Line Items]
Gross loans	$ 3,166,911	$ 1,848,784
Less: Allowance for loan losses	(24,041)	(21,747)	$ (24,460)	$ (29,030)
Net loans	3,142,870	1,827,037
Commercial and Industrial
Financing Receivable Recorded Investment Past Due [Line Items]
Gross loans	715,075	386,233
Less: Allowance for loan losses	(4,461)	(5,309)	(5,135)	(6,600)
Construction
Financing Receivable Recorded Investment Past Due [Line Items]
Gross loans	448,326	245,905
Less: Allowance for loan losses	(7,135)	(4,940)	(5,143)	(3,721)
Residential Real Estate \| 1-to-4 Family Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Gross loans	480,989	294,924
Less: Allowance for loan losses	(3,197)	(3,197)	(4,176)	(6,364)
Residential Real Estate \| Residential Line of Credit
Financing Receivable Recorded Investment Past Due [Line Items]
Gross loans	194,986	177,190
Less: Allowance for loan losses	(944)	(1,613)	(2,201)	(2,790)
Residential Real Estate \| Multi-Family Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Gross loans	62,374	44,977
Less: Allowance for loan losses	(434)	(504)	(311)	(184)
Commercial Real Estate \| Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Gross loans	495,872	357,346
Less: Allowance for loan losses	(3,558)	(3,302)	(3,682)	(6,075)
Commercial Real Estate \| Non-Owner Occupied
Financing Receivable Recorded Investment Past Due [Line Items]
Gross loans	551,588	267,902
Less: Allowance for loan losses	(2,817)	(2,019)	(2,622)	(2,641)
Consumer and Other
Financing Receivable Recorded Investment Past Due [Line Items]
Gross loans	217,701	74,307
Less: Allowance for loan losses	$ (1,495)	$ (863)	$ (1,190)	$ (655)

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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