Fair Value of Financial Instruments - Summary of Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and due from banks	$ 76,441	$ 70,832
Investment securities, held to maturity	200,448	193,194
Loans held for sale	3,094	8,087
Loans excluding loan level hedges, net	2,824,827	2,127,894
Stock in FHLB and FRB	18,105	23,932
Interest receivable	16,244	12,713
Liabilities
Non-interest bearing deposits	601,805	496,248
Interest-bearing deposits	2,279,198	1,974,962
Borrowings	564,157	267,489
Subordinated debentures	37,653	37,456
Interest payable	886	472
Carrying Amount [Member]
Assets
Cash and due from banks	76,441	70,832
Investment securities, held to maturity	200,448	193,194
Loans held for sale	3,094	8,087
Loans excluding loan level hedges, net	2,661,026	1,998,804
Stock in FHLB	18,105
Stock in FHLB and FRB		23,932
Interest receivable	16,244	12,713
Liabilities
Non-interest bearing deposits	601,805	496,248
Interest-bearing deposits	2,279,198	1,974,962
Borrowings	564,157	267,489
Subordinated debentures	37,653	37,456
Interest payable	886	472
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets
Cash and due from banks	76,441	70,832
Liabilities
Non-interest bearing deposits	601,805	496,248
Significant Other Observable Inputs (Level 2) [Member]
Assets
Investment securities, held to maturity	201,085	194,086
Stock in FHLB	18,105
Stock in FHLB and FRB		23,932
Interest receivable	16,244	12,713
Liabilities
Interest-bearing deposits	2,156,487	1,839,167
Borrowings	560,057	261,141
Subordinated debentures	35,994	36,371
Interest payable	886	472
Significant Unobservable Inputs (Level 3) [Member]
Assets
Loans held for sale	3,094	8,087
Loans excluding loan level hedges, net	$ 2,585,879	$ 1,965,928

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For banks and other depository institutions: Includes cash on hand (currency and coin), cash items in process of collection, noninterest bearing deposits due from other financial institutions (including corporate credit unions), and noninterest bearing balances with the Federal Reserve Banks, Federal Home Loan Banks and central banks.

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Represents the aggregate of total long-term debt, including current maturities and short-term debt.

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Fair value of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt.

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Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Amount, after allowance for bad debt, of loan receivables held-for-sale that are not part of a disposal group. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

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