v3.26.1
Debt securities available-for-sale - Schedule of Amortized Cost, Gross Unrealized Gains and Losses, Fair Value, Weighted Average Yield and Contractual Maturities of Debt Securities Available-for-Sale (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Amortized cost    
Amortized cost, Total $ 25,753,421 $ 21,441,599
Gross unrealized gains    
Gross unrealized gains, Total 2,061 35,840
Gross unrealized losses    
Gross unrealized losses, Total 962,648 902,467
Fair value    
Debt securities available-for-sale $ 24,792,834 $ 20,574,972
Weighted average yield    
Weighted average yield, Total 3.23% 3.07%
Debt securities pledged to secure government and trust deposits $ 24,792,834 $ 20,574,972
Asset Pledged as Collateral    
Fair value    
Debt securities available-for-sale 18,900,000 14,300,000
Weighted average yield    
Debt securities pledged to secure government and trust deposits 18,900,000 14,300,000
Debt securities served as collateral for public funds 17,600,000 13,200,000
Asset Not Pledged as Collateral    
Fair value    
Debt securities available-for-sale 5,700,000 6,300,000
Weighted average yield    
Debt securities pledged to secure government and trust deposits 5,700,000 6,300,000
U.S. Treasury securities    
Amortized cost    
Amortized cost - Within 1 year 13,413,909 10,154,698
Amortized cost - After 1 to 5 years 6,928,574 5,555,079
Amortized cost, Total 20,342,483 15,709,777
Gross unrealized gains    
Gross unrealized gains - Within 1 year 338 4,716
Gross unrealized gains - After 1 to 5 years 1,001 29,795
Gross unrealized gains, Total 1,339 34,511
Gross unrealized losses    
Gross unrealized losses - Within 1 year 5,472 1,528
Gross unrealized losses - After 1 to 5 years 67,742 19,306
Gross unrealized losses, Total 73,214 20,834
Fair value    
Fair value - Within 1 year 13,408,775 10,157,886
Fair value - After 1 to 5 years 6,861,833 5,565,568
Debt securities available-for-sale $ 20,270,608 $ 15,723,454
Weighted average yield    
Weighted average yield - Within 1 year 3.56% 3.44%
Weighted average yield - After 1 to 5 years 3.71% 3.70%
Weighted average yield, Total 3.61% 3.53%
Debt securities pledged to secure government and trust deposits $ 20,270,608 $ 15,723,454
Collateralized mortgage obligations - federal agencies    
Amortized cost    
Amortized cost - Within 1 year 44 152
Amortized cost - After 1 to 5 years 2,930 4,879
Amortized cost - After 5 to 10 years 9,680 11,524
Amortized cost - After 10 years 83,627 90,018
Amortized cost, Total 96,281 106,573
Gross unrealized gains    
Gross unrealized gains - Within 1 year 0 0
Gross unrealized gains - After 1 to 5 years 0 0
Gross unrealized gains - After 5 to 10 years 1 0
Gross unrealized gains - After 10 years 45 180
Gross unrealized gains, Total 46 180
Gross unrealized losses    
Gross unrealized losses - Within 1 year 0 1
Gross unrealized losses - After 1 to 5 years 50 88
Gross unrealized losses - After 5 to 10 years 481 482
Gross unrealized losses - After 10 years 6,263 5,941
Gross unrealized losses, Total 6,794 6,512
Fair value    
Fair value - Within 1 year 44 151
Fair value - After 1 to 5 years 2,880 4,791
Fair value - After 5 to 10 years 9,200 11,042
Fair value - After 10 years 77,409 84,257
Debt securities available-for-sale $ 89,533 $ 100,241
Weighted average yield    
Weighted average yield - Within 1 year 5.42% 1.97%
Weighted average yield - After 1 to 5 years 1.48% 1.49%
Weighted average yield - After 5 to 10 years 2.48% 2.45%
Weighted average yield - After 10 years 2.95% 2.92%
Weighted average yield, Total 2.86% 2.80%
Debt securities pledged to secure government and trust deposits $ 89,533 $ 100,241
Mortgage-backed securities - federal agencies    
Amortized cost    
Amortized cost - Within 1 year 477 963
Amortized cost - After 1 to 5 years 101,278 65,843
Amortized cost - After 5 to 10 years 1,028,726 1,030,661
Amortized cost - After 10 years 4,183,655 4,527,032
Amortized cost, Total 5,314,136 5,624,499
Gross unrealized gains    
Gross unrealized gains - Within 1 year 0 1
Gross unrealized gains - After 1 to 5 years 13 11
Gross unrealized gains - After 5 to 10 years 107 256
Gross unrealized gains - After 10 years 556 881
Gross unrealized gains, Total 676 1,149
Gross unrealized losses    
Gross unrealized losses - Within 1 year 3 9
Gross unrealized losses - After 1 to 5 years 3,698 1,530
Gross unrealized losses - After 5 to 10 years 85,945 67,116
Gross unrealized losses - After 10 years 792,994 806,466
Gross unrealized losses, Total 882,640 875,121
Fair value    
Fair value - Within 1 year 474 955
Fair value - After 1 to 5 years 97,593 64,324
Fair value - After 5 to 10 years 942,888 963,801
Fair value - After 10 years 3,391,217 3,721,447
Debt securities available-for-sale $ 4,432,172 $ 4,750,527
Weighted average yield    
Weighted average yield - Within 1 year 2.22% 2.08%
Weighted average yield - After 1 to 5 years 2.14% 2.35%
Weighted average yield - After 5 to 10 years 1.75% 1.85%
Weighted average yield - After 10 years 1.77% 1.75%
Weighted average yield, Total 1.78% 1.78%
Debt securities pledged to secure government and trust deposits $ 4,432,172 $ 4,750,527
Other    
Amortized cost    
Amortized cost - Within 1 year   750
Amortized cost - After 1 to 5 years 521  
Amortized cost, Total 521 750
Gross unrealized gains    
Gross unrealized gains - Within 1 year   0
Gross unrealized gains - After 1 to 5 years 0  
Gross unrealized gains, Total 0 0
Gross unrealized losses    
Gross unrealized losses - Within 1 year   0
Gross unrealized losses - After 1 to 5 years 0  
Gross unrealized losses, Total 0 0
Fair value    
Fair value - Within 1 year   750
Fair value - After 1 to 5 years 521  
Debt securities available-for-sale $ 521 $ 750
Weighted average yield    
Weighted average yield - Within 1 year   4.43%
Weighted average yield - After 1 to 5 years 5.00%  
Weighted average yield, Total 5.00% 4.43%
Debt securities pledged to secure government and trust deposits $ 521 $ 750