Fair Value Accounting - Financial Instruments Measured At Fair Value On A Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Assets
Investment securities available for sale	$ 9,694,515	$ 9,788,662
Mortgage loans held for sale	36,698	47,338
Collateralized mortgage obligations issued by U.S. Government sponsored enterprises
Assets
Investment securities available for sale	564,940	587,595
U.S. Treasury securities
Assets
Investment securities available for sale	615,409	597,629
Mortgage-backed securities issued by U.S. Government agencies
Assets
Investment securities available for sale	911,918	925,664
Mortgage-backed securities issued by U.S. Government sponsored enterprises
Assets
Investment securities available for sale	6,182,911	6,430,379
Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Assets
Investment securities available for sale	1,381,730	1,209,783
Corporate debt securities and other debt securities
Assets
Investment securities available for sale	8,824	8,672
Level 1
Assets
Trading securities	0	0
Investment securities available for sale	615,409	597,629
Other investments	0	0
Mutual funds and mutual funds held in rabbi trusts	59,649	53,742
Derivative assets	0	0
Liabilities
Securities sold short	2,469	3,496
Mutual funds held in rabbi trusts	44,759	38,735
Derivative liabilities	0	0
Level 2
Assets
Trading securities	7,411	12,898
Investment securities available for sale	9,079,106	9,191,033
Other investments	0	0
Mutual funds and mutual funds held in rabbi trusts	0	0
Derivative assets	103,589	94,903
Liabilities
Securities sold short	0	0
Mutual funds held in rabbi trusts	0	0
Derivative liabilities	286,094	259,650
Level 3
Assets
Trading securities	0	0
Investment securities available for sale	0	0
Other investments	13,115	12,560
Mutual funds and mutual funds held in rabbi trusts	0	0
Derivative assets	0	0
Liabilities
Securities sold short	0	0
Mutual funds held in rabbi trusts	0	0
Derivative liabilities	0	0
Fair Value, Measurements, Recurring Basis
Assets
Trading securities	7,411	12,898
Investment securities available for sale	9,694,515	9,788,662
Mortgage loans held for sale	36,698	47,338
Other investments	13,115	12,560
Mutual funds and mutual funds held in rabbi trusts	59,649	53,742
Derivative assets	103,589	94,903
Liabilities
Securities sold short	2,469	3,496
Mutual funds held in rabbi trusts	44,759	38,735
Derivative liabilities	286,094	259,650
Fair Value, Measurements, Recurring Basis \| Collateralized mortgage obligations issued by U.S. Government sponsored enterprises
Assets
Trading securities	2,914	2,910
Investment securities available for sale	564,940	587,595
Fair Value, Measurements, Recurring Basis \| Other mortgage-backed securities
Assets
Trading securities	0	2,149
Fair Value, Measurements, Recurring Basis \| State and municipal securities
Assets
Trading securities	72	0
Fair Value, Measurements, Recurring Basis \| Asset-backed securities
Assets
Trading securities	4,425	7,839
Fair Value, Measurements, Recurring Basis \| U.S. Treasury securities
Assets
Investment securities available for sale	615,409	597,629
Fair Value, Measurements, Recurring Basis \| U.S. Government agency securities
Assets
Investment securities available for sale	28,783	28,940
Fair Value, Measurements, Recurring Basis \| Mortgage-backed securities issued by U.S. Government agencies
Assets
Investment securities available for sale	911,918	925,664
Fair Value, Measurements, Recurring Basis \| Mortgage-backed securities issued by U.S. Government sponsored enterprises
Assets
Investment securities available for sale	6,182,911	6,430,379
Fair Value, Measurements, Recurring Basis \| Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Assets
Investment securities available for sale	1,381,730	1,209,783
Fair Value, Measurements, Recurring Basis \| Corporate debt securities and other debt securities
Assets
Investment securities available for sale	8,824	8,672
Fair Value, Measurements, Recurring Basis \| Level 1
Assets
Trading securities	0	0
Investment securities available for sale	615,409	597,629
Mortgage loans held for sale	0	0
Other investments	0	0
Mutual funds and mutual funds held in rabbi trusts	59,649	53,742
Derivative assets	0	0
Liabilities
Securities sold short	2,469	3,496
Mutual funds held in rabbi trusts	44,759	38,735
Derivative liabilities	0	0
Fair Value, Measurements, Recurring Basis \| Level 1 \| Collateralized mortgage obligations issued by U.S. Government sponsored enterprises
Assets
Trading securities	0	0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring Basis \| Level 1 \| Other mortgage-backed securities
Assets
Trading securities	0	0
Fair Value, Measurements, Recurring Basis \| Level 1 \| State and municipal securities
Assets
Trading securities	0	0
Fair Value, Measurements, Recurring Basis \| Level 1 \| Asset-backed securities
Assets
Trading securities	0	0
Fair Value, Measurements, Recurring Basis \| Level 1 \| U.S. Treasury securities
Assets
Investment securities available for sale	615,409	597,629
Fair Value, Measurements, Recurring Basis \| Level 1 \| U.S. Government agency securities
Assets
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring Basis \| Level 1 \| Mortgage-backed securities issued by U.S. Government agencies
Assets
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring Basis \| Level 1 \| Mortgage-backed securities issued by U.S. Government sponsored enterprises
Assets
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring Basis \| Level 1 \| Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Assets
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring Basis \| Level 1 \| Corporate debt securities and other debt securities
Assets
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring Basis \| Level 2
Assets
Trading securities	7,411	12,898
Investment securities available for sale	9,079,106	9,191,033
Mortgage loans held for sale	36,698	47,338
Other investments	0	0
Mutual funds and mutual funds held in rabbi trusts	0	0
Derivative assets	103,589	94,903
Liabilities
Securities sold short	0	0
Mutual funds held in rabbi trusts	0	0
Derivative liabilities	286,094	259,650
Fair Value, Measurements, Recurring Basis \| Level 2 \| Collateralized mortgage obligations issued by U.S. Government sponsored enterprises
Assets
Trading securities	2,914	2,910
Investment securities available for sale	564,940	587,595
Fair Value, Measurements, Recurring Basis \| Level 2 \| Other mortgage-backed securities
Assets
Trading securities	0	2,149
Fair Value, Measurements, Recurring Basis \| Level 2 \| State and municipal securities
Assets
Trading securities	72	0
Fair Value, Measurements, Recurring Basis \| Level 2 \| Asset-backed securities
Assets
Trading securities	4,425	7,839
Fair Value, Measurements, Recurring Basis \| Level 2 \| U.S. Treasury securities
Assets
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring Basis \| Level 2 \| U.S. Government agency securities
Assets
Investment securities available for sale	28,783	28,940
Fair Value, Measurements, Recurring Basis \| Level 2 \| Mortgage-backed securities issued by U.S. Government agencies
Assets
Investment securities available for sale	911,918	925,664
Fair Value, Measurements, Recurring Basis \| Level 2 \| Mortgage-backed securities issued by U.S. Government sponsored enterprises
Assets
Investment securities available for sale	6,182,911	6,430,379
Fair Value, Measurements, Recurring Basis \| Level 2 \| Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Assets
Investment securities available for sale	1,381,730	1,209,783
Fair Value, Measurements, Recurring Basis \| Level 2 \| Corporate debt securities and other debt securities
Assets
Investment securities available for sale	8,824	8,672
Fair Value, Measurements, Recurring Basis \| Level 3
Assets
Trading securities	0	0
Investment securities available for sale	0	0
Mortgage loans held for sale	0	0
Other investments	13,115	12,560
Mutual funds and mutual funds held in rabbi trusts	0	0
Derivative assets	0	0
Liabilities
Securities sold short	0	0
Mutual funds held in rabbi trusts	0	0
Derivative liabilities	0	0
Fair Value, Measurements, Recurring Basis \| Level 3 \| Collateralized mortgage obligations issued by U.S. Government sponsored enterprises
Assets
Trading securities	0	0
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring Basis \| Level 3 \| Other mortgage-backed securities
Assets
Trading securities	0	0
Fair Value, Measurements, Recurring Basis \| Level 3 \| State and municipal securities
Assets
Trading securities	0	0
Fair Value, Measurements, Recurring Basis \| Level 3 \| Asset-backed securities
Assets
Trading securities	0	0
Fair Value, Measurements, Recurring Basis \| Level 3 \| U.S. Treasury securities
Assets
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring Basis \| Level 3 \| U.S. Government agency securities
Assets
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring Basis \| Level 3 \| Mortgage-backed securities issued by U.S. Government agencies
Assets
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring Basis \| Level 3 \| Mortgage-backed securities issued by U.S. Government sponsored enterprises
Assets
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring Basis \| Level 3 \| Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Assets
Investment securities available for sale	0	0
Fair Value, Measurements, Recurring Basis \| Level 3 \| Corporate debt securities and other debt securities
Assets
Investment securities available for sale	$ 0	$ 0

Mutual Funds And Mutual Funds Held In Rabbi Trusts In Assets

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Mutual Funds And Mutual Funds Held In Rabbi Trusts In Liability

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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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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Fair value portion of mortgage loans held-for-sale.

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Amount of investments classified as other.

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Fair value portion of liabilities pertaining to principal and customer trading transactions, or which may be incurred with the objective of generating a profit from short-term fluctuations in price as part of an entity's market-making, hedging and proprietary trading. Examples include, but are not limited to, short positions in securities, derivatives and commodities.

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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