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Investment Securities (Summary Of Available For Sale Investment Securities By Maturity Groupings) (Details) - USD ($) | Sep. 30, 2022 | Dec. 31, 2021
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 14,176,324,000 | $ 14,419,133,000
Fair Value | 12,632,510,000 | 14,450,027,000
U.S. government and federal agency obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 1,084,984,000 | 1,035,477,000
Fair Value | 1,036,325,000 | 1,080,720,000
U.S. government and federal agency obligations | Within 1 year |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 159,019,000 |
Fair Value | 158,319,000 |
U.S. government and federal agency obligations | After 1 but within 5 years |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 735,831,000 |
Fair Value | 705,287,000 |
U.S. government and federal agency obligations | After 5 but within 10 years |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 190,134,000 |
Fair Value | 172,719,000 |
Government-sponsored enterprise obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 55,737,000 | 50,773,000
Fair Value | 43,175,000 | 51,755,000
Government-sponsored enterprise obligations | After 5 but within 10 years |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 4,987,000 |
Fair Value | 4,545,000 |
Government-sponsored enterprise obligations | After 10 years |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 50,750,000 |
Fair Value | 38,630,000 |
State and Municipal Obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 2,020,984,000 | 2,072,210,000
Fair Value | 1,803,253,000 | 2,096,827,000
State and Municipal Obligations | Within 1 year |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 197,465,000 |
Fair Value | 196,380,000 |
State and Municipal Obligations | After 1 but within 5 years |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 666,078,000 |
Fair Value | 636,464,000 |
State and Municipal Obligations | After 5 but within 10 years |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 936,136,000 |
Fair Value | 787,205,000 |
State and Municipal Obligations | After 10 years |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 221,305,000 |
Fair Value | 183,204,000 |
Agency mortgage-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 5,230,550,000 | 5,698,088,000
Fair Value | 4,445,519,000 | 5,683,000,000
Non-Agency Mortgage-Backed Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 1,449,021,000 | 1,383,037,000
Fair Value | 1,235,584,000 | 1,366,477,000
Asset-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 3,755,855,000 | 3,546,024,000
Fair Value | 3,558,287,000 | 3,539,219,000
Total Mortgage And Asset-Backed Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 10,435,426,000 | 10,627,149,000
Fair Value | 9,239,390,000 | 10,588,696,000
Other debt securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 579,193,000 | 633,524,000
Fair Value | 510,367,000 | $ 632,029,000
Other debt securities | Within 1 year |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 50,783,000 |
Fair Value | 50,639,000 |
Other debt securities | After 1 but within 5 years |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 272,029,000 |
Fair Value | 249,688,000 |
Other debt securities | After 5 but within 10 years |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 247,121,000 |
Fair Value | 202,706,000 |
Other debt securities | After 10 years |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 9,260,000 |
Fair Value | $ 7,334,000 |

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