v3.26.1
Investment Securities (Summary Of Available For Sale Investment Securities By Maturity Groupings) (Details) - USD ($)
Jun. 30, 2026
Dec. 31, 2025
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost $ 8,941,232,000 $ 9,742,278,000
Fair Value 8,322,634,000 9,095,513,000
U.S. government and federal agency obligations    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 3,503,671,000 3,257,561,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost 397,508,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost 1,987,940,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost 913,318,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost 204,905,000  
Fair Value 3,486,809,000 3,279,100,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value 397,509,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value 1,976,364,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value 908,439,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value 204,497,000  
Government-sponsored enterprise obligations    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 54,591,000 54,951,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost 3,962,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost 30,808,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost 19,821,000  
Fair Value 43,849,000 44,712,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value 3,727,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value 26,193,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value 13,929,000  
State and municipal obligations [Member]    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 689,966,000 715,037,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost 62,642,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost 424,901,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost 99,665,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost 102,758,000  
Fair Value 640,224,000 664,733,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value 62,054,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value 404,977,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value 87,676,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value 85,517,000  
Agency mortgage-backed securities    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 3,095,101,000 3,786,811,000
Fair Value 2,602,290,000 3,223,105,000
Non-Agency Mortgage-Backed Securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 416,247,000 467,200,000
Fair Value 385,318,000 435,688,000
Asset-backed securities    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 1,013,942,000 1,269,503,000
Fair Value 1,002,658,000 1,262,045,000
Total Mortgage And Asset-Backed Securities [Member]    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 4,525,290,000 5,523,514,000
Fair Value 3,990,266,000 4,920,838,000
Other debt securities    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 167,714,000 191,215,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost 11,438,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost 51,494,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost 81,368,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost 23,414,000  
Fair Value 161,486,000 $ 186,130,000
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value 11,294,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value 47,691,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value 79,238,000  
Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value $ 23,263,000