Securities - Schedule of Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Amortized Cost And Fair Value Debt Securities [Abstract]
Total available-for-sale debt securities, Amortized Cost, Within one year	$ 25,261
Total available-for-sale debt securities, Amortized Cost, After 1 year through 5 years	159,144
Total available-for-sale debt securities, Amortized Cost, After 5 years through 10 years	307,040
Total available-for-sale debt securities, Amortized Cost, After 10 years	1,946,288
Available-for-sale, Amortized Cost	2,437,733	$ 2,501,188
Total held-to-maturity debt securities, Amortized Cost, Within one year	24,865
Total held-to-maturity debt securities, Amortized Cost, After 1 year through 5 years	111,641
Total held-to-maturity debt securities, Amortized Cost, After 5 years through 10 years	489,993
Total held-to-maturity debt securities, Amortized Cost, After 10 years	563,511
Held-to-maturity, Amortized Cost	1,190,010	1,199,527
Total debt securities, Amortized Cost	3,627,743
Total available-for-sale debt securities, Fair Value, Within one year	24,946
Total available-for-sale debt securities, Fair Value, After 1 year through 5 years	154,948
Total available-for-sale debt securities, Fair Value, After 5 years through 10 years	290,268
Total available-for-sale debt securities, Fair Value, After 10 years	1,649,110
Total available-for-sale debt securities, Fair Value	2,119,272	2,194,329
Total held-to-maturity debt securities, Fair Value, Within one year	24,695
Total held-to-maturity debt securities, Fair Value, After 1 year through 5 years	109,756
Total held-to-maturity debt securities, Fair Value, After 5 years through 10 years	451,150
Total held-to-maturity debt securities, Fair Value, After 10 years	466,843
Total held-to-maturity debt securities, Fair Value	1,052,444	1,069,159
Total debt securities, Fair Value	$ 3,171,716	$ 3,263,488