Fair Value Accounting and Measurement (Carrying Amounts and Estimated Fair Values of Selected Financial Instruments) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets
Interest-earning deposits with banks	$ 706,389	$ 434,867
Debt securities available for sale at fair value	5,496,290	5,210,134
Estimate of Fair Value Measurement [Member]
Assets
Cash and due from banks	178,096	218,899
Interest-earning deposits with banks	706,389	434,867
Debt securities available for sale at fair value	5,496,290	5,210,134
FHLB stock	10,280	10,280
Loans held for sale	26,176	26,481
Loans	9,948,104	9,720,592
Liabilities
Deposits	333,169	338,815
FHLB advances	8,764	9,295
Repurchase agreements	38,624	73,859
Subordinated Debentures	35,102	35,414
Carrying Amount
Assets
Cash and due from banks	178,096	218,899
Interest-earning deposits with banks	706,389	434,867
Debt securities available for sale at fair value	5,496,290	5,210,134
FHLB stock	10,280	10,280
Loans held for sale	26,176	26,481
Loans	9,528,024	9,278,520
Liabilities
Deposits	336,918	338,845
FHLB advances	7,400	7,414
Repurchase agreements	38,624	73,859
Subordinated Debentures	35,046	35,092
Fair Value, Inputs, Level 1 [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Cash and due from banks	178,096	218,899
Interest-earning deposits with banks	706,389	434,867
Debt securities available for sale at fair value	0	0
FHLB stock	0	0
Loans held for sale	0	0
Loans	0	0
Liabilities
Deposits	0	0
FHLB advances	0	0
Repurchase agreements	0	0
Subordinated Debentures	0	0
Fair Value, Inputs, Level 2 [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Cash and due from banks	0	0
Interest-earning deposits with banks	0	0
Debt securities available for sale at fair value	5,496,290	5,210,134
FHLB stock	10,280	10,280
Loans held for sale	26,176	26,481
Loans	0	0
Liabilities
Deposits	333,169	338,815
FHLB advances	8,764	9,295
Repurchase agreements	38,624	73,859
Subordinated Debentures	35,102	35,414
Fair Value, Inputs, Level 3 [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Cash and due from banks	0	0
Interest-earning deposits with banks	0	0
Debt securities available for sale at fair value	0	0
FHLB stock	0	0
Loans held for sale	0	0
Loans	9,948,104	9,720,592
Liabilities
Deposits	0	0
FHLB advances	0	0
Repurchase agreements	0	0
Subordinated Debentures	0	0
Interest Rate Swap \| Estimate of Fair Value Measurement [Member]
Assets
Interest rate derivative asset	32,501	46,184
Liabilities
Interest rate derivative liability	32,769	46,637
Interest Rate Swap \| Carrying Amount
Assets
Interest rate derivative asset	32,501	46,184
Liabilities
Interest rate derivative liability	32,769	46,637
Interest Rate Swap \| Fair Value, Inputs, Level 1 [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Interest rate derivative asset	0	0
Liabilities
Interest rate derivative liability	0	0
Interest Rate Swap \| Fair Value, Inputs, Level 2 [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Interest rate derivative asset	32,501	46,184
Liabilities
Interest rate derivative liability	32,769	46,637
Interest Rate Swap \| Fair Value, Inputs, Level 3 [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Interest rate derivative asset	0	0
Liabilities
Interest rate derivative liability	0	0
Interest Rate Lock Commitments \| Estimate of Fair Value Measurement [Member]
Assets
Interest rate derivative asset	925	1,096
Interest Rate Lock Commitments \| Carrying Amount
Assets
Interest rate derivative asset	925	1,096
Interest Rate Lock Commitments \| Fair Value, Inputs, Level 1 [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Interest rate derivative asset	0	0
Interest Rate Lock Commitments \| Fair Value, Inputs, Level 2 [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Interest rate derivative asset	0	0
Interest Rate Lock Commitments \| Fair Value, Inputs, Level 3 [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Interest rate derivative asset	925	1,096
Forward Sales Contracts \| Estimate of Fair Value Measurement [Member]
Assets
Interest rate derivative asset	505
Liabilities
Interest rate derivative liability		165
Forward Sales Contracts \| Carrying Amount
Assets
Interest rate derivative asset	505
Liabilities
Interest rate derivative liability		165
Forward Sales Contracts \| Fair Value, Inputs, Level 1 [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Interest rate derivative asset	0
Liabilities
Interest rate derivative liability		0
Forward Sales Contracts \| Fair Value, Inputs, Level 2 [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Interest rate derivative asset	505
Liabilities
Interest rate derivative liability		165
Forward Sales Contracts \| Fair Value, Inputs, Level 3 [Member] \| Estimate of Fair Value Measurement [Member]
Assets
Interest rate derivative asset	$ 0
Liabilities
Interest rate derivative liability		$ 0

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Fair value portion 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.

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Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

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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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Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

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For banks and other depository institutions (including Federal Reserve Banks, if applicable): Interest-bearing deposits in other financial institutions for relatively short periods of time including, for example, certificates of deposits, which are presented separately from cash on the balance sheet.

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Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets.

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Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities.

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- Definition

Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.

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- Definition

Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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Fair value portion of securities that an entity sells and agrees to repurchase at a specified date for a specified price.

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