Securities - Amortized Cost and Estimated Fair Value of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Available-for-Sale, Amortized Cost Basis, Due within one year	$ 210,053
Available-for-Sale, Amortized Cost Basis, Due after one year through five years	1,741,024
Available-for-Sale, Amortized Cost Basis, Due after five years through ten years	2,715,108
Available-for-Sale, Amortized Cost Basis, Due after ten years	1,486,163
Available-for-Sale, Amortized Cost Basis, Total	6,152,348	$ 6,447,510
Available-for-Sale, Estimated Fair Value, Due within one year	207,169
Available-for-Sale, Estimated Fair Value, Due after one year through five years	1,632,058
Available-for-Sale, Estimated Fair Value, Due after five years through ten years	2,376,526
Available-for-Sale, Estimated Fair Value, Due after ten years	1,258,606
Securities available-for-sale, Estimated Fair Value, Total	$ 5,474,359	$ 6,573,179