v3.22.4
Securities (Amortized Cost and Estimated Fair Value of Securities Excluding Trading Securities Presented by Contractual Maturity) (Detail) - USD ($)
$ in Thousands
Dec. 31, 2022
Dec. 31, 2021
Schedule of Available-for-Sale Securities [Line Items]    
Held to Maturity, Due in one year or less, Amortized Cost $ 123,591  
Held to Maturity, Due after one year through five years, Amortized Cost 25,839  
Held to Maturity, Due after five years through ten years, Amortized Cost 522,356  
Held to Maturity, Due after ten years, Amortized Cost 1,967,455  
Held to Maturity, Amortized Cost 2,639,241 $ 1,749,337
Held to Maturity, Due in one year or less, Estimated Fair Value 123,505  
Held to Maturity, Due after one year through five years, Estimated Fair Value 25,723  
Held to Maturity, Due after five years through ten years, Estimated Fair Value 459,247  
Held to Maturity, Due after ten years, Estimated Fair Value 1,859,390  
Held to Maturity, Estimated Fair Value 2,467,865 1,809,143
Available for Sale, Due in one year or less, Amortized Cost 510,848  
Available for Sale, Due after one year through five years, Amortized Cost 5,046,852  
Available for Sale, Due after five years through ten years, Amortized Cost 2,387,656  
Available for Sale, Due after ten years, Amortized Cost 11,920,649  
Debt Securities, Available-for-sale, Amortized Cost, Total 19,908,432 13,445,888
Available for Sale, Due in one year or less, Estimated Fair Value 502,257  
Available for Sale, Due after one year through five years, Estimated Fair Value 4,901,648  
Available for Sale, Due after five years through ten years, Estimated Fair Value 2,179,267  
Available for Sale, Due after ten years, Estimated Fair Value 10,618,006  
Debt Securities, Available-for-sale 18,243,605 13,924,628
US Treasury [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Available for Sale, Due in one year or less, Amortized Cost 249,363  
Available for Sale, Due after one year through five years, Amortized Cost 3,574,630  
Available for Sale, Due after five years through ten years, Amortized Cost 1,434,504  
Available for Sale, Due after ten years, Amortized Cost 192,049  
Debt Securities, Available-for-sale, Amortized Cost, Total 5,450,546 2,165,702
Available for Sale, Due in one year or less, Estimated Fair Value 240,361  
Available for Sale, Due after one year through five years, Estimated Fair Value 3,424,023  
Available for Sale, Due after five years through ten years, Estimated Fair Value 1,244,812  
Available for Sale, Due after ten years, Estimated Fair Value 142,391  
Debt Securities, Available-for-sale 5,051,587 2,179,433
Residential Mortgage Backed Securities [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Held to Maturity, Due in one year or less, Amortized Cost 0  
Held to Maturity, Due after one year through five years, Amortized Cost 0  
Held to Maturity, Due after five years through ten years, Amortized Cost 514,059  
Held to Maturity, Due after ten years, Amortized Cost 12,063  
Held to Maturity, Amortized Cost 526,122 527,264
Held to Maturity, Due in one year or less, Estimated Fair Value 0  
Held to Maturity, Due after one year through five years, Estimated Fair Value 0  
Held to Maturity, Due after five years through ten years, Estimated Fair Value 450,961  
Held to Maturity, Due after ten years, Estimated Fair Value 9,839  
Held to Maturity, Estimated Fair Value 460,800 546,030
Available for Sale, Due in one year or less, Amortized Cost 8  
Available for Sale, Due after one year through five years, Amortized Cost 7,729  
Available for Sale, Due after five years through ten years, Amortized Cost 16,025  
Available for Sale, Due after ten years, Amortized Cost 7,293,062  
Debt Securities, Available-for-sale, Amortized Cost, Total 7,316,824 4,059,692
Available for Sale, Due in one year or less, Estimated Fair Value 8  
Available for Sale, Due after one year through five years, Estimated Fair Value 7,527  
Available for Sale, Due after five years through ten years, Estimated Fair Value 15,892  
Available for Sale, Due after ten years, Estimated Fair Value 6,352,809  
Debt Securities, Available-for-sale 6,376,236 4,066,265
States and Political Subdivisions [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Held to Maturity, Due in one year or less, Amortized Cost 123,591  
Held to Maturity, Due after one year through five years, Amortized Cost 24,339  
Held to Maturity, Due after five years through ten years, Amortized Cost 8,297  
Held to Maturity, Due after ten years, Amortized Cost 1,955,392  
Held to Maturity, Amortized Cost 2,111,619 1,220,573
Held to Maturity, Due in one year or less, Estimated Fair Value 123,505  
Held to Maturity, Due after one year through five years, Estimated Fair Value 24,292  
Held to Maturity, Due after five years through ten years, Estimated Fair Value 8,286  
Held to Maturity, Due after ten years, Estimated Fair Value 1,849,551  
Held to Maturity, Estimated Fair Value 2,005,634 1,261,613
Available for Sale, Due in one year or less, Amortized Cost 261,477  
Available for Sale, Due after one year through five years, Amortized Cost 1,464,493  
Available for Sale, Due after five years through ten years, Amortized Cost 937,127  
Available for Sale, Due after ten years, Amortized Cost 4,435,538  
Debt Securities, Available-for-sale, Amortized Cost, Total 7,098,635 7,178,135
Available for Sale, Due in one year or less, Estimated Fair Value 261,888  
Available for Sale, Due after one year through five years, Estimated Fair Value 1,470,098  
Available for Sale, Due after five years through ten years, Estimated Fair Value 918,563  
Available for Sale, Due after ten years, Estimated Fair Value 4,122,806  
Debt Securities, Available-for-sale 6,773,355 7,636,571
Other [Member]    
Schedule of Available-for-Sale Securities [Line Items]    
Held to Maturity, Due in one year or less, Amortized Cost 0  
Held to Maturity, Due after one year through five years, Amortized Cost 1,500  
Held to Maturity, Due after five years through ten years, Amortized Cost 0  
Held to Maturity, Due after ten years, Amortized Cost 0  
Held to Maturity, Amortized Cost 1,500 1,500
Held to Maturity, Due in one year or less, Estimated Fair Value 0  
Held to Maturity, Due after one year through five years, Estimated Fair Value 1,431  
Held to Maturity, Due after five years through ten years, Estimated Fair Value 0  
Held to Maturity, Due after ten years, Estimated Fair Value 0  
Held to Maturity, Estimated Fair Value 1,431 1,500
Available for Sale, Due in one year or less, Amortized Cost 0  
Available for Sale, Due after one year through five years, Amortized Cost 0  
Available for Sale, Due after five years through ten years, Amortized Cost 0  
Available for Sale, Due after ten years, Amortized Cost 0  
Debt Securities, Available-for-sale, Amortized Cost, Total 42,427 42,359
Available for Sale, Due in one year or less, Estimated Fair Value 0  
Available for Sale, Due after one year through five years, Estimated Fair Value 0  
Available for Sale, Due after five years through ten years, Estimated Fair Value 0  
Available for Sale, Due after ten years, Estimated Fair Value 0  
Debt Securities, Available-for-sale $ 42,427 $ 42,359