Fair Value Accounting (Schedule of Financial Instruments Measured at Fair Value on Recurring Basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Assets
Investment securities available for sale	$ 9,621,175	$ 9,678,103
Mortgage loans held for sale	62,616	51,136
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Assets
Investment securities available for sale	615,951	655,127
U.S. Treasury securities
Assets
Investment securities available for sale	473,890	471,813
Mortgage-backed securities issued by U.S. Government agencies
Assets
Investment securities available for sale	817,350	792,749
Mortgage-backed securities issued by U.S. Government sponsored enterprises
Assets
Investment securities available for sale	6,777,393	6,895,070
Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Assets
Investment securities available for sale	879,350	805,945
Corporate debt securities and other debt securities
Assets
Investment securities available for sale	8,638	8,601
Level 1
Assets
Trading securities	0	0
Investment securities available for sale	473,890	471,813
Other investments	0	0
Mutual funds and mutual funds held in rabbi trusts	51,147	42,659
SBA loans servicing asset	0	0
Derivative assets	0	0
Liabilities
Securities sold short	1,461	3,370
Mutual funds held in rabbi trusts	36,380	27,944
Derivative liabilities	0	0
Level 2
Assets
Trading securities	21,467	8,295
Investment securities available for sale	9,147,285	9,206,290
Other investments	0	0
Mutual funds and mutual funds held in rabbi trusts	0	0
SBA loans servicing asset	0	0
Derivative assets	119,659	89,815
Liabilities
Securities sold short	0	0
Mutual funds held in rabbi trusts	0	0
Derivative liabilities	365,390	339,227
Level 3
Assets
Trading securities	0	0
Investment securities available for sale	0	0
Other investments	11,770	11,172
Mutual funds and mutual funds held in rabbi trusts	0	0
SBA loans servicing asset	2,234	2,354
Derivative assets	0	0
Liabilities
Securities sold short	0	0
Mutual funds held in rabbi trusts	0	0
Derivative liabilities	3,937	3,453
Fair Value, Measurements, Recurring Basis
Assets
Trading securities	21,467	8,295
Investment securities available for sale	9,621,175	9,678,103
Mortgage loans held for sale	62,616	51,136
Other investments	11,770	11,172
Mutual funds and mutual funds held in rabbi trusts	51,147	42,659
SBA loans servicing asset	2,234	2,354
Derivative assets	119,659	89,815
Liabilities
Securities sold short	1,461	3,370
Mutual funds held in rabbi trusts	36,380	27,944
Derivative liabilities	369,327	342,680
Fair Value, Measurements, Recurring Basis \| Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Assets
Trading securities	2,875	2,991
Investment securities available for sale	615,951	655,127
Fair Value, Measurements, Recurring Basis \| Other mortgage-backed securities
Assets
Trading securities	2,685	3,185
Fair Value, Measurements, Recurring Basis \| State and municipal securities
Assets
Trading securities	0	48
Fair Value, Measurements, Recurring Basis \| Asset-backed securities
Assets
Trading securities	15,907	2,071
Fair Value, Measurements, Recurring Basis \| U.S. Treasury securities
Assets
Investment securities available for sale	473,890	471,813
Fair Value, Measurements, Recurring Basis \| U.S. Government agency securities
Assets
Investment securities available for sale	48,603	48,798
Fair Value, Measurements, Recurring Basis \| Mortgage-backed securities issued by U.S. Government agencies
Assets
Investment securities available for sale	817,350	792,749
Fair Value, Measurements, Recurring Basis \| Mortgage-backed securities issued by U.S. Government sponsored enterprises
Assets
Investment securities available for sale	6,777,393	6,895,070
Fair Value, Measurements, Recurring Basis \| Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Assets
Investment securities available for sale	879,350	805,945
Fair Value, Measurements, Recurring Basis \| Corporate debt securities and other debt securities
Assets
Investment securities available for sale	8,638	8,601
Fair Value, Measurements, Recurring Basis \| Level 1
Assets
Trading securities	0	0
Investment securities available for sale	473,890	471,813
Mortgage loans held for sale	0	0
Other investments	0	0
Mutual funds and mutual funds held in rabbi trusts	51,147	42,659
SBA loans servicing asset	0	0
Derivative assets	0	0
Liabilities
Securities sold short	1,461	3,370
Mutual funds held in rabbi trusts	36,380	27,944
Derivative liabilities	0	0
Fair Value, Measurements, Recurring Basis \| Level 1 \| Collateralized mortgage obligations issued by U.S. Government agencies or 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	473,890	471,813
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	21,467	8,295
Investment securities available for sale	9,147,285	9,206,290
Mortgage loans held for sale	62,616	51,136
Other investments	0	0
Mutual funds and mutual funds held in rabbi trusts	0	0
SBA loans servicing asset	0	0
Derivative assets	119,659	89,815
Liabilities
Securities sold short	0	0
Mutual funds held in rabbi trusts	0	0
Derivative liabilities	365,390	339,227
Fair Value, Measurements, Recurring Basis \| Level 2 \| Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Assets
Trading securities	2,875	2,991
Investment securities available for sale	615,951	655,127
Fair Value, Measurements, Recurring Basis \| Level 2 \| Other mortgage-backed securities
Assets
Trading securities	2,685	3,185
Fair Value, Measurements, Recurring Basis \| Level 2 \| State and municipal securities
Assets
Trading securities	0	48
Fair Value, Measurements, Recurring Basis \| Level 2 \| Asset-backed securities
Assets
Trading securities	15,907	2,071
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	48,603	48,798
Fair Value, Measurements, Recurring Basis \| Level 2 \| Mortgage-backed securities issued by U.S. Government agencies
Assets
Investment securities available for sale	817,350	792,749
Fair Value, Measurements, Recurring Basis \| Level 2 \| Mortgage-backed securities issued by U.S. Government sponsored enterprises
Assets
Investment securities available for sale	6,777,393	6,895,070
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	879,350	805,945
Fair Value, Measurements, Recurring Basis \| Level 2 \| Corporate debt securities and other debt securities
Assets
Investment securities available for sale	8,638	8,601
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	11,770	11,172
Mutual funds and mutual funds held in rabbi trusts	0	0
SBA loans servicing asset	2,234	2,354
Derivative assets	0	0
Liabilities
Securities sold short	0	0
Mutual funds held in rabbi trusts	0	0
Derivative liabilities	3,937	3,453
Fair Value, Measurements, Recurring Basis \| Level 3 \| Collateralized mortgage obligations issued by U.S. Government agencies or 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 of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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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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