v3.26.1
Investment securities - Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity (Detail) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Debt securities available for sale:    
Due in one year or less $ 750,000  
Due after one year through five years 2,477,000  
Due after five years through ten years 0  
Due after ten years 0  
Total available for sale (amortized cost) 3,227,000  
Mortgage-backed securities 21,992,000  
Investment securities available for sale, amortized cost 25,219,000 $ 22,994,000
Debt securities held to maturity:    
Due in one year or less 409,000  
Due after one year through five years 388,000  
Due after five years through ten years 1,242,000  
Due after ten years 444,000  
Total available for held to maturity (amortized cost) 2,483,000  
Mortgage-backed securities 9,636,000  
Amortized cost for held to maturity 12,119,000 12,430,000
Debt securities available for sale:    
Due in one year or less 753,000  
Due after one year through five years 2,488,000  
Due after five years through ten years 0  
Due after ten years 0  
Total available for sale (fair value) 3,241,000  
Mortgage-backed securities 21,987,000  
Investment securities available for sale, estimated fair value 25,228,000 23,202,000
Debt securities held to maturity:    
Due in one year or less 405,000  
Due after one year through five years 387,000  
Due after five years through ten years 1,217,000  
Due after ten years 406,000  
Total available for held to maturity (fair value) 2,415,000  
Mortgage-backed securities 8,940,000  
Estimated fair value for held to maturity $ 11,355,000 $ 11,715,000