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, 2025	Dec. 31, 2024
Amortized Cost And Fair Value Debt Securities [Abstract]
Total available-for-sale debt securities, Amortized Cost, Within one year	$ 213,602
Total available-for-sale debt securities, Amortized Cost, After 1 year through 5 years	251,380
Total available-for-sale debt securities, Amortized Cost, After 5 years through 10 years	195,460
Total available-for-sale debt securities, Amortized Cost, After 10 years	2,797,718
Available-for-sale, Amortized Cost	3,458,160	$ 2,541,107
Total held-to-maturity debt securities, Amortized Cost, Within one year	34,551
Total held-to-maturity debt securities, Amortized Cost, After 1 year through 5 years	144,258
Total held-to-maturity debt securities, Amortized Cost, After 5 years through 10 years	529,219
Total held-to-maturity debt securities, Amortized Cost, After 10 years	429,754
Held-to-maturity, Amortized Cost	1,137,782	1,152,906
Total debt securities, Amortized Cost	4,595,942	3,694,013
Total available-for-sale debt securities, Fair Value, Within one year	213,581
Total available-for-sale debt securities, Fair Value, After 1 year through 5 years	247,358
Total available-for-sale debt securities, Fair Value, After 5 years through 10 years	185,130
Total available-for-sale debt securities, Fair Value, After 10 years	2,576,750
Total available-for-sale debt securities, Fair Value	3,222,819	2,246,072
Total held-to-maturity debt securities, Fair Value, Within one year	34,511
Total held-to-maturity debt securities, Fair Value, After 1 year through 5 years	141,703
Total held-to-maturity debt securities, Fair Value, After 5 years through 10 years	482,086
Total held-to-maturity debt securities, Fair Value, After 10 years	347,810
Total held-to-maturity debt securities, Fair Value	1,006,110	1,006,817
Total debt securities, Fair Value	$ 4,228,929	$ 3,252,889