Fair Value - Carrying Amounts and Estimated Fair Values of Financial Instruments, Not Carried at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, due from banks, money market, and other interest-earning investments	$ 797,458	$ 589,712
Loans, net	13,476,960	13,655,091
Accrued interest receivable	74,038	85,306
Noninterest-bearing demand deposits	6,440,526	5,633,672
Time deposits	992,837	1,122,870
Federal funds purchased and interbank borrowings	34	1,166
Securities sold under agreements to repurchase	375,247	431,166	$ 399,141
Federal Home Loan Bank advances	1,890,054	1,991,435
Other borrowings	270,968	252,787
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, due from banks, money market, and other interest-earning investments	797,458	589,712
Accrued interest receivable	74,038	85,306
Noninterest-bearing demand deposits	6,440,526	5,633,672
Checking, NOW, savings, and money market interest-bearing deposits	10,762,786	10,280,911
Time deposits	992,837	1,122,870
Federal funds purchased and interbank borrowings	34	1,166
Securities sold under agreements to repurchase	375,247	431,166
Federal Home Loan Bank advances	1,890,054	1,991,435
Other borrowings	270,968	252,787
Accrued interest payable	3,635	5,443
Standby letters of credit	356	462
Commitments to extend credit	0	0
Carrying Value \| Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	3,477,584	3,922,642
Carrying Value \| Commercial real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	6,224,412	5,867,795
Carrying Value \| Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	2,215,256	2,235,814
Carrying Value \| Consumer credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	1,559,708	1,628,840
Estimate of Fair Value Measurement \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, due from banks, money market, and other interest-earning investments	797,458	589,712
Accrued interest receivable	946	21
Noninterest-bearing demand deposits	6,440,526	5,633,672
Checking, NOW, savings, and money market interest-bearing deposits	10,762,786	10,180,911
Time deposits	0	0
Federal funds purchased and interbank borrowings	34	1,166
Securities sold under agreements to repurchase	375,247	431,166
Federal Home Loan Bank advances	0	0
Other borrowings	0	0
Accrued interest payable	0	0
Standby letters of credit	0	0
Commitments to extend credit	0	0
Estimate of Fair Value Measurement \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	0	0
Estimate of Fair Value Measurement \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Commercial real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	0	0
Estimate of Fair Value Measurement \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	0	0
Estimate of Fair Value Measurement \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Consumer credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	0	0
Estimate of Fair Value Measurement \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, due from banks, money market, and other interest-earning investments	0	0
Accrued interest receivable	25,867	27,977
Noninterest-bearing demand deposits	0	0
Checking, NOW, savings, and money market interest-bearing deposits	0	99,957
Time deposits	1,005,601	1,140,922
Federal funds purchased and interbank borrowings	0	0
Securities sold under agreements to repurchase	0	0
Federal Home Loan Bank advances	1,954,334	2,092,033
Other borrowings	288,496	254,612
Accrued interest payable	3,635	5,443
Standby letters of credit	0	0
Commitments to extend credit	0	0
Estimate of Fair Value Measurement \| Significant Other Observable Inputs (Level 2) \| Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	0	0
Estimate of Fair Value Measurement \| Significant Other Observable Inputs (Level 2) \| Commercial real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	0	0
Estimate of Fair Value Measurement \| Significant Other Observable Inputs (Level 2) \| Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	0	0
Estimate of Fair Value Measurement \| Significant Other Observable Inputs (Level 2) \| Consumer credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	0	0
Estimate of Fair Value Measurement \| Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash, due from banks, money market, and other interest-earning investments	0	0
Accrued interest receivable	47,225	57,308
Noninterest-bearing demand deposits	0	0
Checking, NOW, savings, and money market interest-bearing deposits	0	0
Time deposits	0	0
Federal funds purchased and interbank borrowings	0	0
Securities sold under agreements to repurchase	0	0
Federal Home Loan Bank advances	0	0
Other borrowings	0	0
Accrued interest payable	0	0
Standby letters of credit	356	462
Commitments to extend credit	6,824	11,822
Estimate of Fair Value Measurement \| Significant Unobservable Inputs (Level 3) \| Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	3,464,740	3,912,948
Estimate of Fair Value Measurement \| Significant Unobservable Inputs (Level 3) \| Commercial real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	6,146,427	5,797,447
Estimate of Fair Value Measurement \| Significant Unobservable Inputs (Level 3) \| Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	2,209,236	2,264,274
Estimate of Fair Value Measurement \| Significant Unobservable Inputs (Level 3) \| Consumer credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, net	$ 1,578,912	$ 1,618,365

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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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 excluding accrued interest, after allowance for credit loss, of financing receivable.

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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 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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