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Investment Securities (Available For Sale Securities Unrealized Gains And Losses, By Security Type) (Details) - USD ($)
Dec. 31, 2021
Dec. 31, 2020
Investment [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost $ 14,419,133,000 $ 12,097,533,000
Available For Sale Securities, Gross Unreailzed Gain at Period End 163,823,000 358,089,000
Available For Sale Securities, Gross Unrealized Loss at Period End (132,929,000) (6,358,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss 0 0
Debt Securities, Available-for-sale, Fair Value 14,450,027,000 12,449,264,000
U.S. Government And Federal Agency Obligations [Member]    
Investment [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 1,035,477,000 775,592,000
Available For Sale Securities, Gross Unreailzed Gain at Period End 47,484,000 62,467,000
Available For Sale Securities, Gross Unrealized Loss at Period End (2,241,000) 0
Debt Securities, Available-for-sale, Allowance for Credit Loss 0 0
Debt Securities, Available-for-sale, Fair Value 1,080,720,000 838,059,000
US Government-sponsored Enterprise Debt Securities [Member]    
Investment [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 50,773,000 50,803,000
Available For Sale Securities, Gross Unreailzed Gain at Period End 1,901,000 3,780,000
Available For Sale Securities, Gross Unrealized Loss at Period End (919,000) (98,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss 0 0
Debt Securities, Available-for-sale, Fair Value 51,755,000 54,485,000
State and municipal obligations [Member]    
Investment [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 2,072,210,000 1,968,006,000
Available For Sale Securities, Gross Unreailzed Gain at Period End 41,540,000 77,323,000
Available For Sale Securities, Gross Unrealized Loss at Period End (16,923,000) (230,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss 0 0
Debt Securities, Available-for-sale, Fair Value 2,096,827,000 2,045,099,000
Agency mortgage-backed securities [Member]    
Investment [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 5,698,088,000 6,557,098,000
Available For Sale Securities, Gross Unreailzed Gain at Period End 52,676,000 157,789,000
Available For Sale Securities, Gross Unrealized Loss at Period End (67,764,000) (2,802,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss 0 0
Debt Securities, Available-for-sale, Fair Value 5,683,000,000 6,712,085,000
Non-agency mortgage-backed securities [Member]    
Investment [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 1,383,037,000 358,074,000
Available For Sale Securities, Gross Unreailzed Gain at Period End 681,000 3,380,000
Available For Sale Securities, Gross Unrealized Loss at Period End (17,241,000) (380,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss 0 0
Debt Securities, Available-for-sale, Fair Value 1,366,477,000 361,074,000
Asset-backed Securities [Member]    
Investment [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 3,546,024,000 1,853,791,000
Available For Sale Securities, Gross Unreailzed Gain at Period End 12,921,000 31,125,000
Available For Sale Securities, Gross Unrealized Loss at Period End (19,726,000) (2,673,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss 0 0
Debt Securities, Available-for-sale, Fair Value 3,539,219,000 1,882,243,000
Total mortgage and asset-backed securities [Member]    
Investment [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 10,627,149,000 8,768,963,000
Available For Sale Securities, Gross Unreailzed Gain at Period End 66,278,000 192,294,000
Available For Sale Securities, Gross Unrealized Loss at Period End (104,731,000) (5,855,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss 0 0
Debt Securities, Available-for-sale, Fair Value 10,588,696,000 8,955,402,000
Other Debt Securities [Member]    
Investment [Line Items]    
Debt Securities, Available-for-sale, Amortized Cost 633,524,000 534,169,000
Available For Sale Securities, Gross Unreailzed Gain at Period End 6,620,000 22,225,000
Available For Sale Securities, Gross Unrealized Loss at Period End (8,115,000) (175,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss 0 0
Debt Securities, Available-for-sale, Fair Value $ 632,029,000 $ 556,219,000