Fair Value Accounting (Financial Instruments Measured at Fair Value on Recurring Basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets
Investment securities available for sale	$ 9,442,170	$ 7,962,438
Mortgage loans held for sale	202,216	216,647
Mortgage-backed securities issued by U.S. Government agencies
Assets
Investment securities available for sale	976,114	1,218,017
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Assets
Investment securities available for sale	1,104,046	1,250,377
U.S. Treasury securities
Assets
Investment securities available for sale	118,231	20,257
Mortgage-backed securities issued by U.S. Government sponsored enterprises
Assets
Investment securities available for sale	6,708,415	5,000,046
Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Assets
Investment securities available for sale	460,542	370,921
Corporate debt securities and other debt securities
Assets
Investment securities available for sale	18,707	20,500
Level 1
Assets
Trading securities	0	0
Investment securities available for sale	118,231	20,257
Private equity investments	0	0
Mutual funds and mutual funds held in rabbi trusts	41,710	37,650
GGL/SBA loans servicing asset	0	0
Derivative assets	0	0
Liabilities
Trading liability for short positions		0
Earnout liability	0	0
Derivative liabilities	0	0
Level 2
Assets
Trading securities	4,187	10,880
Investment securities available for sale	9,323,939	7,940,160
Private equity investments	0	0
Mutual funds and mutual funds held in rabbi trusts	0	0
GGL/SBA loans servicing asset	0	0
Derivative assets	279,454	401,295
Liabilities
Trading liability for short positions		7,717
Earnout liability	0	0
Derivative liabilities	113,708	155,119
Level 3
Assets
Trading securities	0	0
Investment securities available for sale	0	2,021
Private equity investments	1,026	1,021
Mutual funds and mutual funds held in rabbi trusts	0	0
GGL/SBA loans servicing asset	3,321	3,258
Derivative assets	0	0
Liabilities
Trading liability for short positions		0
Earnout liability	6,427	5,677
Derivative liabilities	1,473	2,048
Fair Value, Measurements, Recurring Basis
Assets
Trading securities	4,187	10,880
Investment securities available for sale	9,442,170	7,962,438
Mortgage loans held for sale	202,216	216,647
Private equity investments	1,026	1,021
Mutual funds and mutual funds held in rabbi trusts	41,710	37,650
GGL/SBA loans servicing asset	3,321	3,258
Derivative assets	279,454	401,295
Liabilities
Trading liability for short positions	0	7,717
Earnout liability	6,427	5,677
Derivative liabilities	115,181	157,167
Fair Value, Measurements, Recurring Basis \| Mortgage-backed securities issued by U.S. Government agencies
Assets
Trading securities	0	10,185
Investment securities available for sale	976,114	1,218,017
Fair Value, Measurements, Recurring Basis \| Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Assets
Trading securities	265	158
Investment securities available for sale	1,104,046	1,250,377
Fair Value, Measurements, Recurring Basis \| Other mortgage-backed securities
Assets
Trading securities	282	178
Fair Value, Measurements, Recurring Basis \| State and municipal securities
Assets
Trading securities	1,495	176
Fair Value, Measurements, Recurring Basis \| Asset-backed securities
Assets
Trading securities	2,145	183
Fair Value, Measurements, Recurring Basis \| U.S. Treasury securities
Assets
Investment securities available for sale	118,231	20,257
Fair Value, Measurements, Recurring Basis \| U.S. Government agency securities
Assets
Investment securities available for sale	56,115	82,320
Fair Value, Measurements, Recurring Basis \| Mortgage-backed securities issued by U.S. Government sponsored enterprises
Assets
Investment securities available for sale	6,708,415	5,000,046
Fair Value, Measurements, Recurring Basis \| Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Assets
Investment securities available for sale	460,542	370,921
Fair Value, Measurements, Recurring Basis \| Corporate debt securities and other debt securities
Assets
Investment securities available for sale	18,707	20,500
Fair Value, Measurements, Recurring Basis \| Level 1
Assets
Trading securities	0	0
Investment securities available for sale	118,231	20,257
Mortgage loans held for sale	0	0
Private equity investments	0	0
Mutual funds and mutual funds held in rabbi trusts	41,710	37,650
GGL/SBA loans servicing asset	0	0
Derivative assets	0	0
Liabilities
Trading liability for short positions	0	0
Earnout liability	0	0
Derivative liabilities	0	0
Fair Value, Measurements, Recurring Basis \| Level 1 \| Mortgage-backed securities issued by U.S. Government agencies
Assets
Trading securities	0	0
Investment securities available for sale	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	118,231	20,257
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 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	4,187	10,880
Investment securities available for sale	9,323,939	7,940,160
Mortgage loans held for sale		216,647
Private equity investments	0	0
Mutual funds and mutual funds held in rabbi trusts	0	0
GGL/SBA loans servicing asset	0	0
Derivative assets	279,454	401,295
Liabilities
Trading liability for short positions	0	7,717
Earnout liability	0	0
Derivative liabilities	113,708	155,119
Fair Value, Measurements, Recurring Basis \| Level 2 \| Mortgage-backed securities issued by U.S. Government agencies
Assets
Trading securities	0	10,185
Investment securities available for sale	976,114	1,218,017
Fair Value, Measurements, Recurring Basis \| Level 2 \| Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Assets
Trading securities	265	158
Investment securities available for sale	1,104,046	1,250,377
Fair Value, Measurements, Recurring Basis \| Level 2 \| Other mortgage-backed securities
Assets
Trading securities	282	178
Fair Value, Measurements, Recurring Basis \| Level 2 \| State and municipal securities
Assets
Trading securities	1,495	176
Fair Value, Measurements, Recurring Basis \| Level 2 \| Asset-backed securities
Assets
Trading securities	2,145	183
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	56,115	82,320
Fair Value, Measurements, Recurring Basis \| Level 2 \| Mortgage-backed securities issued by U.S. Government sponsored enterprises
Assets
Investment securities available for sale	6,708,415	5,000,046
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	460,542	370,921
Fair Value, Measurements, Recurring Basis \| Level 2 \| Corporate debt securities and other debt securities
Assets
Investment securities available for sale	18,707	18,479
Fair Value, Measurements, Recurring Basis \| Level 3
Assets
Trading securities	0	0
Investment securities available for sale	0	2,021
Mortgage loans held for sale	0	0
Private equity investments	1,026	1,021
Mutual funds and mutual funds held in rabbi trusts	0	0
GGL/SBA loans servicing asset	3,321	3,258
Derivative assets	0	0
Liabilities
Trading liability for short positions	0	0
Earnout liability	6,427	5,677
Derivative liabilities	1,473	2,048
Fair Value, Measurements, Recurring Basis \| Level 3 \| Mortgage-backed securities issued by U.S. Government agencies
Assets
Trading securities	0	0
Investment securities available for sale	0	0
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 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	$ 2,021

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Mutual Funds and Mutual Funds Held In Rabbi Trusts

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Private Equity Investments

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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 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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