Estimated Fair Value of Financial Instruments and Fair Value Measurement- Carrying Values and Fair Values of Company's Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Financial Assets:
Investment securities held to maturity, Fair Value	$ 135,085	$ 146,990
Investment securities held to maturity, Carrying Value	135,021	147,614
Federal Home Loan Bank and other membership bank stocks, Fair Value	12,783	15,099
Federal Home Loan Bank and other membership bank stocks, Carrying Value	12,783	15,099
Loans and leases, net Fair Value	4,057,939	3,832,465
Loans and leases, net Carrying Value	4,055,248	3,839,353
Financial Liabilities:
Certificates of deposit, Fair Value	717,318	543,399
Certificates of deposit, Carrying value	720,040	544,908
Other borrowings, Fair Value	195,253	264,586
Other borrowings, Carrying value	196,539	260,866
Subordinated debentures, Fair Value	96,717	94,476
Subordinated debentures, Carrying Value	104,872	104,784
Significant Other Observable Inputs (Level 2) [Member]
Financial Assets:
Investment securities held to maturity, Fair Value	118,002	111,403
Federal Home Loan Bank and other membership bank stocks, Fair Value	12,783	15,099
Financial Liabilities:
Certificates of deposit, Fair Value	717,318	543,399
Other borrowings, Fair Value	195,253	264,586
Significant Unobservable Inputs (Level 3) [Member]
Financial Assets:
Investment securities held to maturity, Fair Value	17,083	35,587
Loans and leases, net Fair Value	4,057,939	3,832,465
Financial Liabilities:
Subordinated debentures, Fair Value	$ 96,717	$ 94,476

Certificate of deposits fair value disclosure.

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Other Borrowings Fair Value Disclosure

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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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Fair value of investments in debt securities classified as held-to-maturity.

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Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.

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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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The carrying amount as of the balance sheet date for the aggregate of other miscellaneous borrowings owed by the reporting entity.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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Amount of time deposit liabilities, including certificates of deposit.

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