Other Borrowings - Narrative (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 25,000,000.0
Outstanding advances	0	$ 0
Unused borrowing capacity	2,100,000,000	1,300,000,000
Unencumbered residential and commercial real estate loans and investment securities pledged	1,600,000,000
Term advances	$ 265,000,000	$ 415,000,000
Weighted average interest rate	2.09%	2.12%
Overnight advances	$ 0	$ 239,100,000
Term advances mature within one year	30,000,000.0
Term advances maturing after one year	235,000,000.0
Maturities of advances due in 2022	85,000,000.0
Maturities of advances due in 2023	80,000,000.0
Maturities of advances due in 2024	70,000,000.0
Callable FHLB borrowings	0
Outstanding on line of credit with bank	0	4,000,000.0
Subsidiaries
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 89,000,000.0	$ 89,000,000.0

Federal Home Loan Bank Advances, Overnight

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Amount of federal home loan bank advances maturing after the next fiscal year following the latest fiscal year.

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No definition available.

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Amount refers to unencumbered residential and commercial real estate loan.

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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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The calculated weighted average interest rate for Federal Home Loan Bank advances outstanding as of the Balance Sheet date.

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Amount of advances or credit lines available from the Federal Home Loan Bank (FHLB).

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Including both current and noncurrent portions, Federal Home Loan Bank borrowings initially due beyond one year or beyond the normal operating cycle if longer.

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Amount of advance from Federal Home Loan Bank (FHLBank) maturing in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of advance from Federal Home Loan Bank (FHLBank) maturing in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of advance from Federal Home Loan Bank (FHLBank) maturing in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of advance from Federal Home Loan Bank (FHLBank) maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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- Definition

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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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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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of borrowings from a bank classified as other, maturing within one year or operating cycle, if longer.

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