v3.22.4
Securities (Year End Securities with Unrealized Losses Segregated by Length of Impairment) (Detail) - USD ($)
$ in Thousands
Dec. 31, 2022
Dec. 31, 2021
Schedule of Available-for-Sale Securities [Line Items]    
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months $ 9,200,946  
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 545,779  
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer 6,217,041  
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss 1,136,206  
Available for Sale, Total Estimated Fair Value 15,417,987  
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax 1,681,985 $ 40,065
US Treasury [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months 2,012,129  
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 63,515  
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer 3,039,458  
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss 335,444  
Available for Sale, Total Estimated Fair Value 5,051,587  
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax 398,959 9,602
Residential Mortgage Backed Securities [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months 3,265,658  
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 345,307  
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer 2,495,906  
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss 603,331  
Available for Sale, Total Estimated Fair Value 5,761,564  
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax 948,638 25,089
States and Political Subdivisions [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months 3,923,159  
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 136,957  
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer 681,677  
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss 197,431  
Available for Sale, Total Estimated Fair Value 4,604,836  
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax $ 334,388 $ 5,374