v3.26.3
Investment Securities - Summary of Continuous Unrealized Loss Position of Securities (Detail) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Schedule of Investments [Line Items]    
Fair Value, Less Than 12 Months, Available-for-sale $ 1,613,121 $ 38,498
Gross Unrealized Holding Losses, Less Than 12 Months, Available-for-sale (50,785) [1] (152)
Fair Value, 12 Months or Longer, Available-for-sale 1,685,247 1,949,268
Gross Unrealized Holding Losses, 12 Months or Longer, Available-for-sale (388,958) [1] (312,213)
Fair Value, Available-for-sale 3,298,368 1,987,766
Gross Unrealized Holding Losses, Available-for-sale (439,743) (312,365)
Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value 114,174 3,690
Gross Unrealized Holding Loss, Less than 12 Months, Held-to-maturity (9,022) [1] (11)
Fair Value, 12 Months or Longer, Held-to-maturity 1,598,236 1,791,972
Gross Unrealized Holding Losses, 12 Months or Longer, Held-to-maturity (451,788) [1] (346,485)
Debt Securities, Held-to-Maturity, Unrealized Loss Position, Fair Value 1,712,410 1,795,662
Gross Unrealized Holding Losses, Held-to-maturity (460,810) (346,496)
CMO/REMIC [Member]    
Schedule of Investments [Line Items]    
Fair Value, Less Than 12 Months, Available-for-sale 615,345 0
Gross Unrealized Holding Losses, Less Than 12 Months, Available-for-sale (15,048) [1] 0
Fair Value, 12 Months or Longer, Available-for-sale 310,039 344,865
Gross Unrealized Holding Losses, 12 Months or Longer, Available-for-sale (127,930) [1] (108,060)
Fair Value, Available-for-sale 925,384 344,865
Gross Unrealized Holding Losses, Available-for-sale (142,978) (108,060)
Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value 0 0
Gross Unrealized Holding Loss, Less than 12 Months, Held-to-maturity 0 [1] 0
Fair Value, 12 Months or Longer, Held-to-maturity 540,395 599,222
Gross Unrealized Holding Losses, 12 Months or Longer, Held-to-maturity (184,437) [1] (152,417)
Debt Securities, Held-to-Maturity, Unrealized Loss Position, Fair Value 540,395 599,222
Gross Unrealized Holding Losses, Held-to-maturity (184,437) (152,417)
Government Agency/GSE [Member]    
Schedule of Investments [Line Items]    
Fair Value, Less Than 12 Months, Available-for-sale 44,893 5,919
Gross Unrealized Holding Losses, Less Than 12 Months, Available-for-sale (152) [1] (81)
Fair Value, 12 Months or Longer, Available-for-sale 0 0
Gross Unrealized Holding Losses, 12 Months or Longer, Available-for-sale 0 [1] 0
Fair Value, Available-for-sale 44,893 5,919
Gross Unrealized Holding Losses, Available-for-sale (152) (81)
Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value 0 0
Gross Unrealized Holding Loss, Less than 12 Months, Held-to-maturity 0 [1] 0
Fair Value, 12 Months or Longer, Held-to-maturity 380,818 415,772
Gross Unrealized Holding Losses, 12 Months or Longer, Held-to-maturity (105,731) [1] (82,741)
Debt Securities, Held-to-Maturity, Unrealized Loss Position, Fair Value 380,818 415,772
Gross Unrealized Holding Losses, Held-to-maturity (105,731) (82,741)
Mortgage-backed Securities [Member]    
Schedule of Investments [Line Items]    
Fair Value, Less Than 12 Months, Available-for-sale 950,317 32,579
Gross Unrealized Holding Losses, Less Than 12 Months, Available-for-sale (35,406) [1] (71)
Fair Value, 12 Months or Longer, Available-for-sale 1,359,153 1,586,803
Gross Unrealized Holding Losses, 12 Months or Longer, Available-for-sale (259,344) [1] (203,629)
Fair Value, Available-for-sale 2,309,470 1,619,382
Gross Unrealized Holding Losses, Available-for-sale (294,750) (203,700)
Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value 20,833 0
Gross Unrealized Holding Loss, Less than 12 Months, Held-to-maturity (1,059) [1] 0
Fair Value, 12 Months or Longer, Held-to-maturity 393,804 455,255
Gross Unrealized Holding Losses, 12 Months or Longer, Held-to-maturity (111,860) [1] (84,512)
Debt Securities, Held-to-Maturity, Unrealized Loss Position, Fair Value 414,637 455,255
Gross Unrealized Holding Losses, Held-to-maturity (112,919) (84,512)
Municipal Bonds [Member]    
Schedule of Investments [Line Items]    
Fair Value, Less Than 12 Months, Available-for-sale 2,566 0
Gross Unrealized Holding Losses, Less Than 12 Months, Available-for-sale (179) [1] 0
Fair Value, 12 Months or Longer, Available-for-sale 16,055 17,600
Gross Unrealized Holding Losses, 12 Months or Longer, Available-for-sale (1,684) [1] (524)
Fair Value, Available-for-sale 18,621 17,600
Gross Unrealized Holding Losses, Available-for-sale (1,863) (524)
Debt Securities, Held-to-Maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value 93,341 3,690
Gross Unrealized Holding Loss, Less than 12 Months, Held-to-maturity (7,963) [1] (11)
Fair Value, 12 Months or Longer, Held-to-maturity 283,219 321,723
Gross Unrealized Holding Losses, 12 Months or Longer, Held-to-maturity (49,760) [1] (26,815)
Debt Securities, Held-to-Maturity, Unrealized Loss Position, Fair Value 376,560 325,413
Gross Unrealized Holding Losses, Held-to-maturity $ (57,723) $ (26,826)
[1] The gross unrealized holding losses of available-for-sale securities excludes the portfolio layer fair value hedge basis adjustments of $23.6 million at September 30, 2026.