Average term extended for letters of credit, in years.

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Amount of interest expense expected to be recognized during the next fiscal year following the latest fiscal year for the gain on termination of forward interest rate locks.

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Amount of contingent liability related to off balance sheet commitments, including letters of credit, the entity entered into. Included in other liabilities in the balance sheet.

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Maximum period the entity is hedging its exposure to the variability in future cash flows for forecasted transaction.

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The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

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The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Face (par) amount of debt instrument at time of issuance.

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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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No definition available.

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The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

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Nominal or face amount used to calculate payment on derivative.

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Amount before tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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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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Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Average period extended for letter of credit	1 year
Loan commitments and letters of credit	$ 5,600,000	$ 2,700,000
Net liability position, derivative instruments	500,000
Collateral already posted	0
Additional collateral required	500,000
Net unrealized gains (losses) arising during the year		(1,700,000)	$ (1,000,000.0)
Interest Rate Swaps [Member] \| Subordinated Notes [Member]
Derivative [Line Items]
Notional Amounts	585,000,000.0	585,000,000.0
Interest Rate Swaps [Member] \| Cash Flow [Member] \| Loans [Member]
Derivative [Line Items]
Notional Amounts	210,000,000
Interest Rate Swaps [Member] \| Fair Value [Member]
Derivative [Line Items]
Notional Amounts	375,000,000
Subordinated notes	$ 400,000,000
Basis points	1.265%
Treasury Forward Interest Rate Locks ("T-Locks") [Member]
Derivative [Line Items]
Period hedged items affected earnings, years	10 years
Net unrealized gains (losses) arising during the year	$ 900,000
Total unrecognized gain	100,000	$ 100,000
Treasury Forward Interest Rate Locks ("T-Locks") [Member] \| Subordinated Notes [Member]
Derivative [Line Items]
Senior notes issuance	$ 500,000,000