Securities - Schedule of Unrealized Losses on Investment Securities (Detail) $ in Thousands	Jun. 30, 2022 USD ($) Security	Dec. 31, 2021 USD ($) Security
Net Unrealized Gains And Losses On Investments [Line Items]
Less than 12 months, Fair Value	$ 2,131,784	$ 1,825,891
Less than 12 months, Unrealized Losses	$ (151,715)	$ (31,548)
Less than 12 months, Number of Securities | Security	586	187
12 months or more, Fair Value	$ 619,275	$ 252,725
12 months or more, Unrealized Losses	$ (80,664)	$ (5,227)
12 months or more, Number of Securities | Security	86	35
Fair Value, Total	$ 2,751,059	$ 2,078,616
Unrealized Losses, Total	$ (232,379)	$ (36,775)
Number of Securities Total | Security	672	222
U.S. Government Sponsored Entities and Agencies [Member]
Net Unrealized Gains And Losses On Investments [Line Items]
Less than 12 months, Fair Value	$ 188,621	$ 114,486
Less than 12 months, Unrealized Losses	$ (13,338)	$ (1,865)
Less than 12 months, Number of Securities | Security	36	12
12 months or more, Fair Value	$ 49,739	$ 32,688
12 months or more, Unrealized Losses	$ (8,962)	$ (1,175)
12 months or more, Number of Securities | Security	6	4
Fair Value, Total	$ 238,360	$ 147,174
Unrealized Losses, Total	$ (22,300)	$ (3,040)
Number of Securities Total | Security	42	16
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	$ 1,575,495	$ 1,568,138
Less than 12 months, Unrealized Losses	$ (131,223)	$ (29,060)
Less than 12 months, Number of Securities | Security	415	143
12 months or more, Fair Value	$ 482,704	$ 141,681
12 months or more, Unrealized Losses	$ (69,889)	$ (3,386)
12 months or more, Number of Securities | Security	60	23
Fair Value, Total	$ 2,058,199	$ 1,709,819
Unrealized Losses, Total	$ (201,112)	$ (32,446)
Number of Securities Total | Security	475	166
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	$ 306,173	$ 131,970
Less than 12 months, Unrealized Losses	$ (4,152)	$ (579)
Less than 12 months, Number of Securities | Security	47	25
12 months or more, Fair Value	$ 86,832	$ 78,356
12 months or more, Unrealized Losses	$ (1,813)	$ (666)
12 months or more, Number of Securities | Security	20	8
Fair Value, Total	$ 393,005	$ 210,326
Unrealized Losses, Total	$ (5,965)	$ (1,245)
Number of Securities Total | Security	67	33
Obligations of State and Political Subdivisions [Member]
Net Unrealized Gains And Losses On Investments [Line Items]
Less than 12 months, Fair Value	$ 51,167	$ 4,307
Less than 12 months, Unrealized Losses	$ (2,830)	$ (35)
Less than 12 months, Number of Securities | Security	81	2
Fair Value, Total	$ 51,167	$ 4,307
Unrealized Losses, Total	$ (2,830)	$ (35)
Number of Securities Total | Security	81	2
Corporate Debt and Other Securities [Member]
Net Unrealized Gains And Losses On Investments [Line Items]
Less than 12 months, Fair Value	$ 10,328	$ 6,990
Less than 12 months, Unrealized Losses	$ (172)	$ (9)
Less than 12 months, Number of Securities | Security	7	5
Fair Value, Total	$ 10,328	$ 6,990
Unrealized Losses, Total	$ (172)	$ (9)
Number of Securities Total | Security	7	5