Investment Securities - Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Debt securities available for sale:
Due in one year or less	$ 8,067
Due after one year through five years	5,344,779
Due after five years through ten years	79,469
Due after ten years	30,000
Total available for sale (amortized cost)	5,462,315
Mortgage-backed securities available for sale	3,417,101
Investment securities available for sale, amortized cost	8,879,416	$ 3,849,347
Debt securities held to maturity:
Due in one year or less	382,222
Due after one year through five years	1,180,314
Due after five years through ten years	946,218
Due after ten years	1,566,704
Total available for held to maturity (amortized cost)	4,075,458
Mortgage-backed securities held to maturity	9,297,713
Amortized cost for held to maturity	13,373,171	2,734,674
Debt securities available for sale:
Due in one year or less	8,024
Due after one year through five years	5,251,402
Due after five years through ten years	77,014
Due after ten years	26,962
Total available for sale (fair value)	5,363,402
Mortgage-backed securities available for sale	3,341,553
Total	8,704,955	3,955,804
Debt securities held to maturity:
Due in one year or less	381,067
Due after one year through five years	1,162,783
Due after five years through ten years	928,727
Due after ten years	1,476,398
Total available for held to maturity (fair value)	3,948,975
Mortgage-backed securities held to maturity	8,747,140
Total	$ 12,696,115	$ 2,771,290