Fair Value Measurement - Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands		Sep. 30, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)		$ 1,424,562	$ 2,764,325
Derivative assets	[1]	7,032	13,412
Derivative liabilities	[1]	22,804	2,194
US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)			58,877
State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)		1,038,332	2,051,936
Corporate bonds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)		57,417	135,532
Residential MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)	[2]	320,368	426,350
Commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)	[2]	8,445	91,630
Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments		5,224	5,920
Total asset fair value measurements		1,517,866	2,788,476
Total liability fair value measurements		22,822	19,823
Fair Value, Recurring | US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)			58,877
Fair Value, Recurring | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)		1,038,332	2,051,936
Fair Value, Recurring | Corporate bonds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)		57,417	135,532
Fair Value, Recurring | Residential MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)	[3]	320,368	426,350
Fair Value, Recurring | Commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)	[3]	8,445	91,630
Fair Value, Recurring | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		88,080	18,231
Derivative liabilities		22,822	19,823
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments		5,224	5,920
Total asset fair value measurements		5,224	64,797
Total liability fair value measurements		0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)			58,877
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)		0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)		0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Residential MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)	[3]	0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)	[3]	0	0
Fair Value, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0	0
Derivative liabilities		0	0
Fair Value, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments		0	0
Total asset fair value measurements		1,512,642	2,723,679
Total liability fair value measurements		22,822	19,823
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)			0
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)		1,038,332	2,051,936
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)		57,417	135,532
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Residential MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)	[3]	320,368	426,350
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)	[3]	8,445	91,630
Fair Value, Recurring | Significant Other Observable Inputs (Level 2) | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		88,080	18,231
Derivative liabilities		22,822	19,823
Fair Value, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments		0	0
Total asset fair value measurements		0	0
Total liability fair value measurements		0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)			0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | State and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)		0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Corporate bonds and other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)		0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Residential MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)	[3]	0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Commercial MBS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS, at estimated fair value (amortized cost of $1,592,891 and $2,655,594, respectively)	[3]	0	0
Fair Value, Recurring | Significant Unobservable Inputs (Level 3) | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0	0
Derivative liabilities		0	0
Fair Value, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreclosed assets		197
Total asset fair value measurements		8,421	8,458
Fair Value, Nonrecurring | Collateral-dependent loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral-dependent loans	[4]	8,224	8,458
Fair Value, Nonrecurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreclosed assets		0
Total asset fair value measurements		0	0
Fair Value, Nonrecurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Collateral-dependent loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral-dependent loans	[4]	0	0
Fair Value, Nonrecurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreclosed assets		0
Total asset fair value measurements		0	0
Fair Value, Nonrecurring | Significant Other Observable Inputs (Level 2) | Collateral-dependent loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral-dependent loans	[4]	0	0
Fair Value, Nonrecurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreclosed assets		197
Total asset fair value measurements		8,421	8,458
Fair Value, Nonrecurring | Significant Unobservable Inputs (Level 3) | Collateral-dependent loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral-dependent loans	[4]	$ 8,224	$ 8,458

[1] Net derivative assets are included in other assets and net derivative liabilities are included in other liabilities on the consolidated balance sheets. Included in the fair value of net derivative assets and net derivative liabilities are credit valuation adjustments reflecting counterparty credit risk and our credit risk. We had $7.0 million credit exposure related to interest rate swaps with financial institutions and none related to interest rate swaps with customers at September 30, 2022. We had no credit exposure related to interest rate swaps with financial institutions and $13.4 million related to interest rate swaps with customers at December 31, 2021. The credit risk associated with customer transactions is partially mitigated as these are generally secured by the non-cash collateral securing the underlying transaction being hedged.

[2] All MBS are issued and/or guaranteed by U.S. government agencies or U.S. GSEs.

[3] All MBS are issued and/or guaranteed by U.S. government agencies or U.S. GSEs.

[4] Consists of individually evaluated loans. Loans for which the fair value of the collateral and commercial real estate fair value of the properties is less than cost basis are presented net of allowance. Losses on these loans represent charge-offs which are netted against the allowance for loan losses.