Fair Value - Carrying Amounts and Estimated Fair Values of Financial Instruments, Not Carried at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, due from banks, money market, and other interest-earning investments	$ 420,250	$ 317,165	$ 286,761
Investment securities held to maturity	407,281	506,334	512,207
Loans, net	12,017,648	12,243,892	11,292,659
Accrued interest receivable	80,747	89,464	78,493
Noninterest-bearing demand deposits	3,996,264	3,965,380	3,588,370
Time deposits	1,830,063	2,024,256	1,892,135
Federal funds purchased and interbank borrowings	240,589	270,135	450,031
Securities sold under agreements to repurchase	337,551	362,294	319,831
Federal Home Loan Bank advances	2,001,960	1,613,481	1,554,515
Other borrowings	251,763	247,883	251,662
Mortgage-Backed Securities - Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities held to maturity	112,187	127,120
States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities held to maturity	261,773	305,228
Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	5,112,123	4,958,851	4,481,554
Consumer Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	1,718,343	1,803,667	1,695,625
Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	2,950,559	3,232,970	2,949,277
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, due from banks, money market, and other interest-earning investments	420,250	317,165
Accrued interest receivable	34	13
Noninterest-bearing demand deposits	3,996,264	3,965,380
Checking, NOW, savings, and money market interest-bearing deposits	8,622,025	8,360,313
Federal funds purchased and interbank borrowings	240,589	270,135
Securities sold under agreements to repurchase	337,551	362,294
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accrued interest receivable	24,183	27,580
Time deposits	1,842,750	2,002,187
Federal Home Loan Bank advances	2,007,228	1,611,103
Other borrowings	262,921	248,065
Accrued interest payable	7,107	9,871
Significant Other Observable Inputs (Level 2) [Member] \| U.S. Government-Sponsored Entities and Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities held to maturity	34,446	72,359
Significant Other Observable Inputs (Level 2) [Member] \| Mortgage-Backed Securities - Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities held to maturity	115,767	124,409
Significant Other Observable Inputs (Level 2) [Member] \| States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities held to maturity	275,375	309,335
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accrued interest receivable	56,530	61,871
Standby letters of credit	573	525
Commitments to extend credit	5,925	3,115
Significant Unobservable Inputs (Level 3) [Member] \| Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	5,046,715	4,781,294
Significant Unobservable Inputs (Level 3) [Member] \| Consumer Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	1,671,597	1,773,352
Significant Unobservable Inputs (Level 3) [Member] \| Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	2,882,142	3,161,132
Residential Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	2,236,623	2,248,404	$ 2,166,203
Residential Real Estate [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	2,246,971	2,225,853
Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, due from banks, money market, and other interest-earning investments	420,250	317,165
Accrued interest receivable	80,747	89,464
Noninterest-bearing demand deposits	3,996,264	3,965,380
Checking, NOW, savings, and money market interest-bearing deposits	8,622,025	8,360,313
Time deposits	1,830,063	2,024,256
Federal funds purchased and interbank borrowings	240,589	270,135
Securities sold under agreements to repurchase	337,551	362,294
Federal Home Loan Bank advances	2,001,960	1,613,481
Other borrowings	251,763	247,883
Accrued interest payable	7,107	9,871
Standby letters of credit	573	525
Carrying Value [Member] \| U.S. Government-Sponsored Entities and Agencies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities held to maturity	33,321	73,986
Carrying Value [Member] \| Mortgage-Backed Securities - Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities held to maturity	112,187	127,120
Carrying Value [Member] \| States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities held to maturity	261,773	305,228
Carrying Value [Member] \| Commercial Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	5,087,869	4,935,381
Carrying Value [Member] \| Consumer Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	1,710,179	1,795,695
Carrying Value [Member] \| Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	2,928,430	3,211,228
Carrying Value [Member] \| Residential Real Estate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	$ 2,234,260	$ 2,246,127

Checking, NOW, savings, and money market interest-bearing deposits.

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Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The fair value of financial liabilities, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

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Amount of short term borrowing where a bank borrows, at the federal funds rate, from another bank.

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

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Amount of interest payable on debt, including, but not limited to, trade payables.

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Amount before allowance and after 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.

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Amount of domestic noninterest-bearing deposits held by the entity, which may include demand deposits, checking, brokered and retail deposits.

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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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Amount, after the effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Amount of time deposit liabilities, including certificates of deposit.

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