Fair Value Measurements - Assets and Liabilities Measured at Estimated Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available For Sale Securities Debt Securities	$ 10,870,346	$ 3,955,804
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading account	129,672	49,545
Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading account		200
U.S. Treasury and Federal Agencies [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available For Sale Securities Debt Securities	7,658,728	678,690
Commercial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available For Sale Securities Debt Securities	606,571
Residential [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available For Sale Securities Debt Securities	2,430,946	3,155,312
Other Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available For Sale Securities Debt Securities	174,101	121,802
Fair Value Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading account	129,672	49,745
Available For Sale Securities Debt Securities	10,870,346	3,955,804
Equity Securities Fv Ni	194,537	77,640
Real estate loans held for sale	342,720	899,282
Other assets	491,867	442,453
Total assets	12,029,142	5,424,924
Other liabilities	1,481,364	93,843
Total liabilities	1,481,364	93,843
Fair Value Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading account	129,672	49,545
Equity Securities Fv Ni	184,811	68,850
Total assets	314,483	118,395
Fair Value Measurements, Recurring [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Trading account		200
Available For Sale Securities Debt Securities	10,870,346	3,955,804
Equity Securities Fv Ni	9,726	8,790
Real estate loans held for sale	342,720	899,282
Other assets	491,024	430,725
Total assets	11,713,816	5,294,801
Other liabilities	1,432,215	88,555
Total liabilities	1,432,215	88,555
Fair Value Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other assets	843	11,728
Total assets	843	11,728
Other liabilities	49,149	5,288
Total liabilities	49,149	5,288
Fair Value Measurements, Recurring [Member] | U.S. Treasury and Federal Agencies [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available For Sale Securities Debt Securities	7,658,728	678,690
Fair Value Measurements, Recurring [Member] | U.S. Treasury and Federal Agencies [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available For Sale Securities Debt Securities	7,658,728	678,690
Fair Value Measurements, Recurring [Member] | Commercial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available For Sale Securities Debt Securities	606,571
Fair Value Measurements, Recurring [Member] | Commercial [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available For Sale Securities Debt Securities	606,571
Fair Value Measurements, Recurring [Member] | Residential [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available For Sale Securities Debt Securities	2,430,946	3,155,312
Fair Value Measurements, Recurring [Member] | Residential [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available For Sale Securities Debt Securities	2,430,946	3,155,312
Fair Value Measurements, Recurring [Member] | Other Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available For Sale Securities Debt Securities	174,101	121,802
Fair Value Measurements, Recurring [Member] | Other Debt Securities [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available For Sale Securities Debt Securities	$ 174,101	$ 121,802