v3.25.2
Investment Securities (Summary Of Available For Sale Investment Securities By Maturity Groupings) (Details) - USD ($)
Jun. 30, 2025
Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost $ 9,680,135,000 $ 10,127,426,000
Fair Value 8,915,779,000 9,136,853,000
U.S. government and federal agency obligations    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 2,586,856,000 2,594,130,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost 439,321,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost 1,429,778,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost 717,757,000  
Fair Value 2,597,737,000 2,555,252,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value 439,782,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value 1,437,921,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value 720,034,000  
Government-sponsored enterprise obligations    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 55,032,000 55,425,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost 35,212,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost 19,820,000  
Fair Value 44,148,000 42,849,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value 30,195,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value 13,953,000  
State and municipal obligations [Member]    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 774,740,000 822,790,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost 70,837,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost 416,047,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost 176,358,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost 111,498,000  
Fair Value 714,958,000 742,891,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value 70,298,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value 393,723,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value 155,555,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value 95,382,000  
Agency mortgage-backed securities    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 3,991,521,000 4,195,182,000
Fair Value 3,356,039,000 3,444,891,000
Non-Agency Mortgage-Backed Securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 539,853,000 625,539,000
Fair Value 499,996,000 568,689,000
Asset-backed securities    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 1,516,911,000 1,595,797,000
Fair Value 1,496,323,000 1,557,015,000
Total Mortgage And Asset-Backed Securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 6,048,285,000 6,416,518,000
Fair Value 5,352,358,000 5,570,595,000
Other debt securities    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 215,222,000 238,563,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost 24,459,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost 73,750,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost 92,265,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost 24,748,000  
Fair Value 206,578,000 $ 225,266,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value 24,152,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value 68,648,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value 89,325,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value $ 24,453,000