Investment Securities - Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Debt securities available for sale:
Due in one year or less	$ 6,886
Due after one year through five years	7,979,072
Due after five years through ten years	74,469
Due after ten years	30,000
Total available for sale (amortized cost)	8,090,427
Mortgage-backed securities available for sale	3,249,728
Investment securities available for sale, amortized cost	11,340,155	$ 3,849,347
Debt securities held to maturity:
Due in one year or less	292,223
Due after one year through five years	1,096,658
Due after five years through ten years	1,045,507
Due after ten years	1,430,873
Total available for held to maturity (amortized cost)	3,865,261
Mortgage-backed securities held to maturity	9,033,601
Amortized cost for held to maturity	12,898,862	2,734,674
Debt securities available for sale:
Due in one year or less	6,813
Due after one year through five years	7,727,233
Due after five years through ten years	71,558
Due after ten years	27,225
Total available for sale (fair value)	7,832,829
Mortgage-backed securities available for sale	3,037,517
Total	10,870,346	3,955,804
Debt securities held to maturity:
Due in one year or less	290,088
Due after one year through five years	1,045,997
Due after five years through ten years	992,244
Due after ten years	1,265,674
Total available for held to maturity (fair value)	3,594,003
Mortgage-backed securities held to maturity	7,960,652
Total	$ 11,554,655	$ 2,771,290