Securities - Schedule of Amortized Cost and Fair Value of Available-for-Sale and Held-to-Maturity Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Amortized Cost And Fair Value Debt Securities [Abstract]
Total available-for-sale debt securities, Amortized Cost, Within one year	$ 31,190
Total available-for-sale debt securities, Amortized Cost, After 1 year through 5 years	153,759
Total available-for-sale debt securities, Amortized Cost, After 5 years through 10 years	474,806
Total available-for-sale debt securities, Amortized Cost, After 10 years	2,336,698
Available-for-sale, Amortized Cost	2,996,453	$ 3,019,695
Total held-to-maturity debt securities, Amortized Cost, Within one year	26,906
Total held-to-maturity debt securities, Amortized Cost, After 1 year through 5 years	99,676
Total held-to-maturity debt securities, Amortized Cost, After 5 years through 10 years	350,392
Total held-to-maturity debt securities, Amortized Cost, After 10 years	785,493
Held-to-maturity, Amortized Cost	1,262,467	1,004,823
Total debt securities, Amortized Cost	4,258,920
Total available-for-sale debt securities, Fair Value, Within one year	30,874
Total available-for-sale debt securities, Fair Value, After 1 year through 5 years	149,576
Total available-for-sale debt securities, Fair Value, After 5 years through 10 years	452,056
Total available-for-sale debt securities, Fair Value, After 10 years	2,013,242
Total available-for-sale debt securities, Fair Value	2,645,748	3,013,462
Total held-to-maturity debt securities, Fair Value, Within one year	26,820
Total held-to-maturity debt securities, Fair Value, After 1 year through 5 years	97,773
Total held-to-maturity debt securities, Fair Value, After 5 years through 10 years	321,926
Total held-to-maturity debt securities, Fair Value, After 10 years	619,314
Total held-to-maturity debt securities, Fair Value	1,065,833	1,028,452
Total debt securities, Fair Value	$ 3,711,581	$ 4,041,914