Securities - Schedule of Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Amortized Cost And Fair Value Debt Securities [Abstract]
Total available-for-sale debt securities, Amortized Cost, Within one year	$ 75,322
Total available-for-sale debt securities, Amortized Cost, After 1 year through 5 years	170,101
Total available-for-sale debt securities, Amortized Cost, After 5 years through 10 years	295,411
Total available-for-sale debt securities, Amortized Cost, After 10 years	1,879,947
Available-for-sale, Amortized Cost	2,420,781	$ 2,501,188
Total held-to-maturity debt securities, Amortized Cost, Within one year	22,438
Total held-to-maturity debt securities, Amortized Cost, After 1 year through 5 years	114,612
Total held-to-maturity debt securities, Amortized Cost, After 5 years through 10 years	501,534
Total held-to-maturity debt securities, Amortized Cost, After 10 years	541,100
Held-to-maturity, Amortized Cost	1,179,684	1,199,527
Total debt securities, Amortized Cost	3,600,465	3,700,715
Total available-for-sale debt securities, Fair Value, Within one year	75,127
Total available-for-sale debt securities, Fair Value, After 1 year through 5 years	165,339
Total available-for-sale debt securities, Fair Value, After 5 years through 10 years	278,986
Total available-for-sale debt securities, Fair Value, After 10 years	1,582,671
Total available-for-sale debt securities, Fair Value	2,102,123	2,194,329
Total held-to-maturity debt securities, Fair Value, Within one year	22,325
Total held-to-maturity debt securities, Fair Value, After 1 year through 5 years	112,057
Total held-to-maturity debt securities, Fair Value, After 5 years through 10 years	453,682
Total held-to-maturity debt securities, Fair Value, After 10 years	440,368
Total held-to-maturity debt securities, Fair Value	1,028,432	1,069,159
Total debt securities, Fair Value	$ 3,130,555	$ 3,263,488