Securities - Schedule of Unrealized Losses on Investment Securities (Detail) $ in Thousands	Jun. 30, 2025 USD ($) Security	Dec. 31, 2024 USD ($) Security
Net Unrealized Gains And Losses On Investments [Line Items]
Less than 12 months, Fair Value	$ 435,336	$ 223,438
Less than 12 months, Unrealized Losses	$ (2,393)	$ (1,966)
Less than 12 months, Number of Securities | Security	116	47
12 months or more, Fair Value	$ 1,716,219	$ 1,850,875
12 months or more, Unrealized Losses	$ (239,773)	$ (293,453)
12 months or more, Number of Securities | Security	590	626
Fair Value, Total	$ 2,151,555	$ 2,074,313
Unrealized Losses, Total	$ (242,166)	$ (295,419)
Number of Securities Total | Security	706	673
US Treasury Securities [Member]
Net Unrealized Gains And Losses On Investments [Line Items]
Less than 12 months, Fair Value	$ 98,756	$ 48,846
Less than 12 months, Unrealized Losses	$ (35)	$ (63)
Less than 12 months, Number of Securities | Security	3	2
Fair Value, Total	$ 98,756	$ 48,846
Unrealized Losses, Total	$ (35)	$ (63)
Number of Securities Total | Security	3	2
U.S. Government Sponsored Entities and Agencies [Member]
Net Unrealized Gains And Losses On Investments [Line Items]
12 months or more, Fair Value	$ 193,534	$ 194,242
12 months or more, Unrealized Losses	$ (23,601)	$ (30,702)
12 months or more, Number of Securities | Security	43	43
Fair Value, Total	$ 193,534	$ 194,242
Unrealized Losses, Total	$ (23,601)	$ (30,702)
Number of Securities Total | Security	43	43
Residential Mortgage-Backed Securities and Collateralized Mortgage Obligations of Government Sponsored Entities and Agencies [Member]
Net Unrealized Gains And Losses On Investments [Line Items]
Less than 12 months, Fair Value	$ 224,629	$ 149,466
Less than 12 months, Unrealized Losses	$ (1,290)	$ (1,742)
Less than 12 months, Number of Securities | Security	54	32
12 months or more, Fair Value	$ 1,351,335	$ 1,408,115
12 months or more, Unrealized Losses	$ (210,167)	$ (255,346)
12 months or more, Number of Securities | Security	440	447
Fair Value, Total	$ 1,575,964	$ 1,557,581
Unrealized Losses, Total	$ (211,457)	$ (257,088)
Number of Securities Total | Security	494	479
Commercial Mortgage-Backed Securities and Collateralized Mortgage Obligations of Government Sponsored Entities and Agencies [Member]
Net Unrealized Gains And Losses On Investments [Line Items]
Less than 12 months, Fair Value	$ 6,750	$ 9,919
Less than 12 months, Unrealized Losses	$ (7)	$ (7)
Less than 12 months, Number of Securities | Security	3	1
12 months or more, Fair Value	$ 125,035	$ 193,085
12 months or more, Unrealized Losses	$ (3,367)	$ (4,135)
12 months or more, Number of Securities | Security	37	50
Fair Value, Total	$ 131,785	$ 203,004
Unrealized Losses, Total	$ (3,374)	$ (4,142)
Number of Securities Total | Security	40	51
Asset-Backed Securities [Member]
Net Unrealized Gains And Losses On Investments [Line Items]
Less than 12 months, Fair Value	$ 61,449
Less than 12 months, Unrealized Losses	$ (642)
Less than 12 months, Number of Securities | Security	12
Fair Value, Total	$ 61,449
Unrealized Losses, Total	$ (642)
Number of Securities Total | Security	12
Obligations of State and Political Subdivisions [Member]
Net Unrealized Gains And Losses On Investments [Line Items]
Less than 12 months, Fair Value	$ 15,961	$ 10,728
Less than 12 months, Unrealized Losses	$ (281)	$ (133)
Less than 12 months, Number of Securities | Security	24	8
12 months or more, Fair Value	$ 40,868	$ 48,038
12 months or more, Unrealized Losses	$ (2,605)	$ (3,191)
12 months or more, Number of Securities | Security	68	84
Fair Value, Total	$ 56,829	$ 58,766
Unrealized Losses, Total	$ (2,886)	$ (3,324)
Number of Securities Total | Security	92	92
Corporate Debt Securities [Member]
Net Unrealized Gains And Losses On Investments [Line Items]
Less than 12 months, Fair Value	$ 27,791	$ 4,479
Less than 12 months, Unrealized Losses	$ (138)	$ (21)
Less than 12 months, Number of Securities | Security	20	4
12 months or more, Fair Value	$ 5,447	$ 7,395
12 months or more, Unrealized Losses	$ (33)	$ (79)
12 months or more, Number of Securities | Security	2	2
Fair Value, Total	$ 33,238	$ 11,874
Unrealized Losses, Total	$ (171)	$ (100)
Number of Securities Total | Security	22	6