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, 2019	Dec. 31, 2018
Financial Assets:
Investment securities held to maturity	$ 151,115	$ 153,646
Investment securities held to maturity, Fair Value	152,495	150,932
Federal Home Loan Bank and other membership bank stocks, Carrying Value	18,006	13,301
Federal Home Loan Bank and other membership bank stocks, Fair Value	18,006	13,301
Loans and leases, net Carrying Value	4,884,759	4,419,045
Loans and leases, net Fair Value	4,964,970	4,341,477
Financial Liabilities:
Certificates of deposit, Carrying value	913,213	757,038
Certificates of deposit, Fair Value	913,550	750,801
Other borrowings, Carrying value	165,818	181,118
Other borrowings, Fair Value	166,581	176,921
Subordinated debentures, Carrying Value	118,211	105,027
Subordinated debentures, Fair Value	116,160	102,497
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial Assets:
Investment securities held to maturity, Fair Value	0	0
Federal Home Loan Bank and other membership bank stocks, Fair Value	0	0
Loans and leases, net Fair Value	0	0
Financial Liabilities:
Certificates of deposit, Fair Value	0	0
Other borrowings, Fair Value	0	0
Subordinated debentures, Fair Value	0	0
Significant Other Observable Inputs (Level 2)
Financial Assets:
Investment securities held to maturity, Fair Value	149,093	143,913
Federal Home Loan Bank and other membership bank stocks, Fair Value	18,006	13,301
Loans and leases, net Fair Value	0	0
Financial Liabilities:
Certificates of deposit, Fair Value	913,550	750,801
Other borrowings, Fair Value	166,581	176,921
Subordinated debentures, Fair Value	0	0
Significant Unobservable Inputs (Level 3)
Financial Assets:
Investment securities held to maturity, Fair Value	3,402	7,019
Federal Home Loan Bank and other membership bank stocks, Fair Value	0	0
Loans and leases, net Fair Value	4,964,970	4,341,477
Financial Liabilities:
Certificates of deposit, Fair Value	0	0
Other borrowings, Fair Value	0	0
Subordinated debentures, Fair Value	$ 116,160	$ 102,497

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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 of investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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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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